Transcript
LT1227 140MHz Video Current Feedback Amplifier
FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■
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■
DESCRIPTIO
140MHz Bandwidth: AV = 2, RL = 150Ω 1100V/µs Slew Rate Low Cost 30mA Output Drive Current 0.01% Differential Gain 0.01° Differential Phase High Input Impedance: 14MΩ, 3pF Wide Supply Range: ±2V to ±15V Shutdown Mode: IS < 250µA Low Supply Current: IS = 10mA Inputs Common Mode to Within 1.5V of Supplies Outputs Swing Within 0.8V of Supplies
■ ■ ■ ■
A shutdown feature switches the device into a high impedance, low current mode, allowing multiple devices to be connected in parallel and selected. Input to output isolation in shutdown is 70dB at 10MHz for input amplitudes up to 10VP-P. The shutdown pin interfaces to open collector or open drain logic and takes only 4µs to enable or disable. The LT1227 comes in the industry standard pinout and can upgrade the performance of many older products. For a dual or quad version, see the LT1229/1230 data sheet.
U APPLICATIO S ■
The LT®1227 is a current feedback amplifier with wide bandwidth and excellent video characteristics. The low differential gain and phase, wide bandwidth, and 30mA output drive current make the LT1227 well suited to drive cables in video systems.
Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers 50Ω Buffers for Driving Mixers
The LT1227 is manufactured on Linear Technology’s proprietary complementary bipolar process. , LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
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Video Cable Driver
Differential Gain and Phase vs Supply Voltage 0.20
+
75Ω LT1227 75Ω CABLE
RF 1k
VOUT VOUT =1 VIN
75Ω
0.16
0.16
0.12
0.12
0.08
0.08 ∆φ
DIFFERENTIAL GAIN (%)
–
RG 1k
0.20 NTSC COMPOSITE f = 3.58MHz
DIFFERENTIAL PHASE (DEG)
VIN
0.04
0.04
1227 TA01
∆G 0
5
7
11 13 9 SUPPLY VOLTAGE (±V)
15
0
LT1227 • TA02
1
LT1227
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RATI GS
W
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PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage ..................................................... ±18V Input Current ...................................................... ±15mA Output Short Circuit Duration (Note 2) ........ Continuous Operating Temperature Range LT1227C .................................................. 0°C to 70°C LT1227M (OBSOLETE) .................... – 55°C to 125°C Storage Temperature Range ................. – 65°C to 150°C Junction Temperature Plastic Package ................................................ 150°C Ceramic Package (OBSOLETE) ........................ 175°C Lead Temperature (Soldering, 10 sec.)................ 300°C
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ABSOLUTE
ORDER PART NUMBER
TOP VIEW NULL 1
8 SHDN
LT1227CN8
–IN 2
7 V+
+IN 3
6 OUT
V– 4
5 NULL
N8 PACKAGE 8-LEAD PLASTIC DIP TJMAX = 150°C, θJA = 100°C/W (N) J8 PACKAGE 8-LEAD CERAMIC DIP TJMAX = 175°C, θJA = 100°C/W (J)
LT1227MJ8
OBSOLETE PACKAGE Consider the N8 Package for Alternate Source.
ORDER PART NUMBER
TOP VIEW NULL 1
8 SHDN
–IN 2
7 V+
+IN 3
6
V– 4
LT1227CS8
OUT
5 NULL
S8 PART MARKING
S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 150°C/W
1227
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. SYMBOL VOS
PARAMETER Input Offset Voltage
IIN+
Input Offset Voltage Drift Noninverting Input Current
CONDITIONS TA = 25°C
MIN
TYP ±3
●
10 ±0.3
●
TA = 25°C ●
IIN–
Inverting Input Current
±10
TA = 25°C ●
en +in –in RIN
Input Noise Voltage Density Noninverting Input Noise Current Density Inverting Input Noise Current Density Input Resistance
CIN
Input Capacitance Input Voltage Range
f = 1kHz, RF = 1k, RG = 10Ω, RS = 0Ω f = 1kHz f = 1kHz VIN = ±13V, VS = ±15V VIN = ±3V, VS = ±5V
● ●
VS = ±15V, TA = 25°C ●
VS = ±5V, TA = 25°C ●
CMRR
2
Common Mode Rejection Ratio
VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±3V, TA = 25°C VS = ±5V, VCM = ±2V
● ●
1.5 1.5 ±13 ±12 ±3 ±2 55 55 55 55
3.2 1.7 32 14 11 3 ±13.5 ±3.5 62 61
MAX ±10 ±15 ±3 ±10 ±60 ±100
UNITS mV mV µV/°C µA µA µA µA nV/√Hz pA/√Hz pA/√Hz MΩ MΩ pF V V V V dB dB dB dB
LT1227
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. SYMBOL
PSRR
PARAMETER Inverting Input Current Common Mode Rejection
Power Supply Rejection Ratio
AV
Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection Large-Signal Voltage Gain
ROL
Transresistance, ∆VOUT/∆IIN–
VOUT
Maximum Output Voltage Swing
CONDITIONS VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±3V, TA = 25°C VS = ±5V, VCM = ±2V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ±2V, RL = 150Ω VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ±2V, RL = 150Ω VS = ±15V, RL = 400Ω, TA = 25°C
MIN ●
4.5 ● ●
0.25 ● ● ● ● ●
●
RL = 0Ω, TA = 25°C VS = ±15V, VOUT = 0V, TA = 25°C
55 55 100 100 ±12 ±10 ±3 ±2.5 30
VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C
±3.7 60 10 120
●
I8 SR tr, tf BW tr, tf
tS
Shutdown Pin Current (Note 4) Output Leakage Current, Shutdown Slew Rate (Notes 5 and 6) Rise and Fall Time, VOUT = 1VP-P Small-Signal Bandwidth Small-Signal Rise and Fall Time Propagation Delay Small-Signal Overshoot Settling Time Differential Gain (Note 7) Differential Phase (Note 7)
VS = ±15V VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C TA = 25°C VS = ±5V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω 0.1%, VOUT = 10V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: A heat sink may be required depending on the power supply voltage. Note 3: The supply current of the LT1227 has a negative temperature coefficient. For more information, see Typical Performance Characteristics curves.
●
500
50 50 5 5
72 72 270 240 ±13.5
●
Positive Supply Current, Shutdown
MAX 10 10 10 10
80 2
●
Maximum Output Current Supply Current (Note 3)
60 60
●
VS = ±5V, RL = 150Ω, TA = 25°C IOUT IS
TYP 3.5
1100 8.7 140 3.3 3.4 5 50 0.014 0.010 0.010 0.013
15.0 17.5 300 500 300 10
UNITS µA/V µA/V µA/V µA/V dB dB nA/V nA/V µA/V µA/V dB dB kΩ kΩ V V V V mA mA mA µA µA µA µA V/µs ns MHz ns ns % ns % % DEG DEG
Note 4: Ramp Pin 8 voltage down from 15V while measuring IS. When IS drops to less than 0.5mA, measure Pin 8 current. Note 5: Slew rate is measured at ±5V on a ±10V output signal while operating on ±15V supplies with RF = 2k, RG = 220Ω and R L = 400Ω. Note 6: AC parameters are 100% tested on the ceramic and plastic DIP package parts (J and N suffix) and are sample tested on every lot of the SO packaged parts (S suffix). Note 7: NTSC composite video with an output level of 2V.
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LT1227 TYPICAL PERFOR A CE CHARACTERISTICS U W
Voltage Gain and Phase vs Frequency, Gain = 6dB
135
225
4 3 VS = ±15V RL = 100Ω RF = 910Ω
1 0 0.1
RF = 750Ω
100 RF = 1k
80 60 40
RF = 2k
20 0 1 10 FREQUENCY (MHz)
100
0
2
4
6 8 10 12 14 SUPPLY VOLTAGE (±V)
LT1227 • TPC01
135
20
180
GAIN
225
18 17 16
VS = ±15V RL = 100Ω RF = 825Ω
15 14 0.1
120 100
RF = 250Ω
RF = 500Ω
80
RF = 750Ω
60
RF = 1k
40
0
VOLTAGE GAIN (dB)
41
135
40
180 225
38 37 36 35 34 0.1
VS = ±15V RL = 100Ω RF = 500Ω
RF = 2k
100
18
140 120
80
RF = 750Ω
60
RF = 1k
40
0 0
2
4
6 8 10 12 14 SUPPLY VOLTAGE (±V)
RF = 500Ω
100
16
18
RF = 2k 0
2
4
6 8 10 12 14 SUPPLY VOLTAGE (±V)
16
16
14
14
RF = 500Ω RF = 1k
10 RF = 2k
8
18
–3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 1k 18
12
16
LT1227 • TPC06
18
6 4
0 1 10 FREQUENCY (MHz)
16
PEAKING ≤ 0.5dB PEAKING ≤ 5dB
20
RF = 500Ω
12
RF = 1k
RF = 2k
10 8 6 4 2
2
LT1227 • TPC07
4
PHASE SHIFT (DEG)
90
–3dB BANDWIDTH (MHz)
0 45
42
39
6 8 10 12 14 SUPPLY VOLTAGE (±V)
LT1227 • TPC03
–3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 100Ω
GAIN
4
LT1227 • TPC05
Voltage Gain and Phase vs Frequency, Gain = 40dB PHASE
2
–3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 1k
140
100
44
0
160
LT1227 • TPC04
43
40
180
20
1 10 FREQUENCY (MHz)
RF = 1k
60
0
18
PEAKING ≤ 0.5dB PEAKING ≤ 5dB
160
–3dB BANDWIDTH (MHz)
VOLTAGE GAIN (dB)
90
21
PHASE SHIFT (DEG)
45
22
19
16
180
0 PHASE
RF = 1.5k
80
–3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 100Ω
24
RF = 2k
100
LT1227 • TPC02
Voltage Gain and Phase vs Frequency, Gain = 20dB 23
RF = 750Ω
140 120
20
–3dB BANDWIDTH (MHz)
2
RF = 500Ω
–3dB BANDWIDTH (MHz)
5
180
GAIN
140 120
PEAKING ≤ 0.5dB PEAKING ≤ 5dB
160 –3dB BANDWIDTH (MHz)
90
7
180 PEAKING ≤ 0.5dB PEAKING ≤ 5dB
160 –3dB BANDWIDTH (MHz)
VOLTAGE GAIN (dB)
45
PHASE SHIFT (DEG)
PHASE
8
6
180
0
10 9
–3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 1k
–3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 100Ω
0
0
2
4
6 8 10 12 14 SUPPLY VOLTAGE (±V)
16
18
LT1227 • TPC08
0
2
4
6 8 10 12 14 SUPPLY VOLTAGE (±V)
16
18
LT1227 • TPC09
LT1227 TYPICAL PERFOR A CE CHARACTERISTICS U W
Total Harmonic Distortion vs Frequency 0.1
RL = 1k PEAKING ≤ 5dB GAIN = 2 CAPACITIVE LOAD (pF)
1000
TOTAL HARMONIC DISTORTION (%)
10000
VS = ±5V
VS = ±15V
100
10
2 1 FEEDBACK RESISTOR (kΩ)
0
3
25
VS = ±15V RL = 400Ω RF = RG = 1k
0.01
OUTPUT SATURATION VOLTAGE (V)
COMMON MODE RANGE (V)
–1.5 –2.0
2.0 1.5 V – = –2V TO –18V
–0.5
50 25 0 75 TEMPERATURE (°C)
100
–1.0
1.0 0.5 V– –50 –25
125
50 25 75 0 TEMPERATURE (°C)
POWER SUPPLY REJECTION (dB)
SPOT NOISE (nV/√Hz OR pA/√Hz)
80
–in
10
en +in 1 100
1k 10k FREQUENCY (Hz)
50
40
30 –50 –25
125
100k LT1227 • TPC16
25 50 75 100 125 150 175 TEMPERATURE (°C)
0
LT1227 • TPC15
Power Supply Rejection vs Frequency
100
10
100
60
LT1227 • TPC14
LT1227 • TPC13
Spot Noise Voltage and Current vs Frequency
Output Impedance vs Frequency
60 POSITIVE NEGATIVE
20
0 10k
100
VS = ±15V RL = 100Ω RF = RG = 1k
40
100
70
RL = ∞ ±2V ≤ VS ≤ ±18V
VS = ±15V
10 OUTPUT IMPEDANCE (Ω)
–25
10 FREQUENCY (MHz)
Output Short-Circuit Current vs Junction Temperature
0.5 V– –50
1
LT1127 • TPC12
OUTPUT SHORT-CIRCUIT CURRENT (mA)
V+
V+
1.0
100k
Output Saturation Voltage vs Temperature
V + = 2V TO 18V
AV = +2
LT1227 • TPC11
Input Common Mode Limit vs Temperature
–1.0
AV = +1
10
0
1k 10k FREQUENCY (Hz)
LT1227 • TPC10
–0.5
AV = +10 AV = –1
15
5
VO = 1VRMS
100
VS = ±15V RL = 1k RF = 1k
20
VO = 7VRMS
0.001 10
1
Maximum Undistorted Output vs Frequency
OUTPUT VOLTAGE (VP-P)
Maximum Capacitive Load vs Feedback Resistor
1
RF = RG = 2k RF = RG = 1k
0.1
0.01
100k
1M 10M FREQUENCY (Hz)
100M LT1227 • TPC17
0.001 10k
100k
1M 10M FREQUENCY (Hz)
100M
LT1227 • TPC18
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LT1227 TYPICAL PERFOR A CE CHARACTERISTICS U W
Settling Time to 1mV vs Output Step
Settling Time to 10mV vs Output Step 10
VS = ±15V RF = RG = 1k
8
13 12
4
NONINVERTING
2
INVERTING
0 –2 –4
4 2 NONINVERTING
0
INVERTING
–2 –4
8
–8
5
60 40 SETTLING TIME (ns)
80
–10
100
4
4
0
12 16 8 SETTLING TIME (µs)
(VO)DC = 0.5V 1.0V 1.5V 2.0V
0.05 0.10
0.20
VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k
0.30 100k
100M
1M
10M
2ND 3RD
–50
VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k
0.06 100k
1M
–60
10M
LT1227 • TPC24
Test Circuit for 3rd Order Intercept
VS = ±15V RL = 100Ω RF = 680Ω RG = 75Ω
40
100M
FREQUENCY (Hz)
3rd Order Intercept vs Frequency
3RD ORDER INTERCEPT (dBm)
–40
0.04
LT1227 • TPC23
45
VS = ±15V VO = 2VP-P RL = 100Ω RF = 820Ω AV = 10dB
–30
100M
(VO)DC = 0.5V 1.0V 2.0V
0.03
0.05
LT1227 • TPC22
–20
18
0.02
FREQUENCY (Hz)
2nd and 3rd Harmonic Distortion vs Frequency
16
0.01
0.15
0.25
1M 10M FREQUENCY (Hz)
6 8 10 12 14 SUPPLY VOLTAGE (±V)
0
DIFFERENTIAL GAIN (%)
1
4
Differential Gain vs Frequency
0
DIFFERENTIAL PHASE (DEG)
10
2
0
LT1227 • TPC21
Differential Phase vs Frequency
VS = ±15V AV = 1 RF = 1.5k
0.1 100k
20
175°C
LT1227 • TPC20
Output Impedance in Shutdown vs Frequency 100
125°C
7
–8 20
25°C
9
6
LT1227 • TPC19
OUTPUT IMPEDANCE (kΩ)
10
–6
0
–55°C
11
–6
–10
DISTORTION (dBc)
SUPPLY CURRENT (mA)
6 OUTPUT STEP (V)
OUTPUT STEP (V)
VS = ±15V RF = RG = 1k
8
6
Supply Current vs Supply Voltage 14
10
+
50Ω LT1227
35
PO
– 680Ω
30 25
75Ω
50Ω
MEASURE INTERCEPT AT PO
20
1227 TC
–70
1
10 FREQUENCY (MHz)
100 LT1227 • TPC25
6
15
0
10
20 30 40 FREQUENCY (MHz)
50
60
LT1227 • TPC26
LT1227 W
SI PLIFIED SCHE ATIC W
7
14k
NULL 1
V+
NULL 5
CURRENT SOURCE BIAS
8 S/D +IN 3
2
–IN
6 VOUT
4 V– 1227 SS
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APPLICATI
The LT1227 is a very fast current feedback amplifier. Because it is a current feedback amplifier, the bandwidth is maintained over a wide range of voltage gains. The amplifier is designed to drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The small-signal bandwidth of the LT1227 is set by the external feedback resistors and the internal junction capacitors. As a result, the bandwidth is a function of the supply voltage, the value of the feedback resistor, the closed-loop gain and load resistor. The characteristic curves of Bandwidth vs Supply Voltage show the effect of a heavy load (100Ω) and a light load (1k). These curves use a solid line when the response has less than 0.5dB of peaking and a dashed line when the response has 0.5dB to
5dB of peaking. The curves stop where the response has more than 5dB of peaking. At a gain of two, on ±15V supplies with a 1k feedback resistor, the bandwidth into a light load is over 140MHz, but into a heavy load the bandwidth reduces to 120MHz. The loading has this effect because there is a mild resonance in the output stage that enhances the bandwidth at light loads but has its Q reduced by the heavy load. This enhancement is only useful at low gain settlings; at a gain of ten it does not boost the bandwidth. At unity gain, the enhancement is so effective the value of the feedback resistor has very little effect. At very high closed-loop gains, the bandwidth is limited by the gain bandwidth product of about 1GHz. The curves show that the bandwidth at a closed-loop gain of 100 is 12MHz, only one tenth what it is at a gain of two.
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LT1227 W
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and inverting input bias current will change. The offset voltage changes about 500µV per volt of supply mismatch. The inverting bias current can change as much as 5.0µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt.
Small-Signal Rise Time, AV = +2
Slew Rate
VOUT
RF = 1k, RG= 1k, RL = 100Ω
AI01
Capacitance on the Inverting Input Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response (and overshoot in the transient response), but it does not degrade the stability of the amplifier. Capacitive Loads The LT1227 can drive capacitive loads directly when the proper value of feedback resistor is used. The graph of Maximum Capacitive Load vs Feedback Resistor should be used to select the appropriate value. The value shown is for 5dB peaking when driving a 1k load at a gain of 2. This is a worst case condition, the amplifier is more stable at higher gains and driving heavier loads. Alternatively, a small resistor (10Ω to 20Ω) can be put in series with the output to isolate the capacitive load from the amplifier output. This has the advantage that the amplifier bandwidth is only reduced when the capacitive load is present and the disadvantage that the gain is a function of the load resistance.
The slew rate of a current feedback amplifier is not independent of the amplifier gain configuration the way slew rate is in a traditional op amp. This is because both the input stage and the output stage have slew rate limitations. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude between the input pins is small and the overall slew rate is that of the output stage. For gains less than ten in the noninverting mode, the overall slew rate is limited by the input stage. The input stage slew rate of the LT1227 is approximately 125V/µs and is set by internal currents and capacitances. The output slew rate is set by the value of the feedback resistors and the internal capacitances. At a gain of ten with a 1k feedback resistor and ±15V supplies, the output slew rate is typically 1100V/µs. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The graph of Maximum Undistorted Output vs Frequency relates the slew rate limitations to sinusoidal inputs for various gain configurations. Large-Signal Transient Response, AV = +10
VOUT
Power Supplies The LT1227 will operate from single or split supplies from ±2V (4V total) to ±15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage
8
RF = 910Ω, RG= 100Ω, RL = 400Ω
AI02
LT1227 W
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Shutdown
Large-Signal Transient Response, AV = +2
VOUT
RF = 1k, RG= 1k, RL = 400Ω
AI03
Large-Signal Transient Response, AV = –2
The LT1227 has a high impedance, low supply current mode which is controlled by Pin 8. In the shutdown mode, the output looks like a 12pF capacitor and the supply current drops to approximately the Pin 8 current. The shutdown pin is referenced to the positive supply through an internal pullup circuit (see the simplified schematic). Pulling a current of greater than 50µA from Pin 8 will put the device into the shutdown mode. An easy way to force shutdown is to ground Pin 8, using open drain (collector) logic. Because the pin is referenced to the positive supply, the logic used should have a breakdown voltage of greater than the positive supply voltage. No other circuitry is necessary as an internal JFET limits the Pin 8 current to about 100µA. When Pin 8 is open, the LT1227 operates normally. Differential Input Signal Swing
VOUT
AI04
RF = 1k, RG= 510Ω, RL = 400Ω
AI04
The differential input swing is limited to about ±6V by an ESD protection device connected between the inputs. In normal operation, the differential voltage between the input pins is small, so this clamp has no effect; however, in the shutdown mode, the differential swing can be the same as the input swing. The clamp voltage will then set the maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than ±5V when the device is shutdown. Offset Adjust
Settling Time The characteristic curves show that the LT1227 amplifier settles to within 10mV of final value in 40ns to 55ns for any output step up to 10V. The curve of settling to 1mV of final value shows that there is a slower thermal contribution up to 20µs. The thermal settling component comes from the output and the input stage. The output contributes just under 1mV per volt of output change and the input contributes 300µV per volt of input change. Fortunately the input thermal tends to cancel the output thermal. For this reason the noninverting gain of two configuration settles faster than the inverting gain of one.
Pins 1 and 5 are provided for offset nulling. A small current to V + or ground will compensate for DC offsets in the device. The pins are referenced to the positive supply (see the simplified schematic) and should be left open if unused. The offset adjust pins act primarily on the inverting input bias current. A 10k pot connected to Pins 1 and 5 with the wiper connected to V + will null out the bias current, but will not affect the offset voltage much. Since the output offset is VO ≅ AV • VOS + (IIN –) • RF at higher gains (AV > 5), the VOS term will dominate. To null out the VOS term, use a 10k pot between Pins 1 and 5 with a 150k resistor from the wiper to ground for 15V split supplies, 47k for 5V split supplies.
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LT1227
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S MUX Amplifier
MUX Amplifier The shutdown function can be effectively used to construct a MUX amplifier. A two-channel version is shown, but more inputs could be added with suitable logic. By configuring each amplifier as a unity-gain follower, there is no loading by the feedback network when the amplifier is off. The open drains of the 74C906 buffers are used to interface the 5V logic to the shutdown pin. Feedthrough from the unselected input to the output is –70dB at 10MHz. The differential voltage between MUX inputs VIN1 and VIN2 appears across the inputs of the shutdown device, this voltage should be less than ±5V to avoid turning on the clamp diodes discussed previously. If the inputs are sinusoidal having a zero DC level, this implies that the amplitude of each input should be less than 5VP-P. The output impedance of the off amplifier remains high until the output level exceeds approximately 6VP-P at 10MHz, this sets the maximum usable output level. Switching time between inputs is about 4µs without an external pullup. Adding a 10k pullup resistor from each shutdown pin to V + will reduce the switching time to 2µs but will increase the positive supply current in shutdown by 1.5mA.
15V
+
VIN1
LT1227 S/D
VOUT
– –15V 1.5k
VOUT =1 VIN
5V
74C906
15V
+
VIN2
LT1227 S/D
– –15V 1.5k 5V
5V INPUT SELECT
74HC04
74C906 1227 TA04
MUX Output MUX Input Crosstalk vs Frequency –40
INPUT CROSSTALK (dB)
–50 VOUT
INPUT SELECT
–60
–70
–80
–90 VIN1 = 1VP-P, VIN2 = 0V
TA03
1
10 FREQUENCY (MHz)
100 LT1227 TA05
10
LT1227 U PACKAGE DESCRIPTIO J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110)
0.300 BSC (0.762 BSC)
0.008 – 0.018 (0.203 – 0.457)
CORNER LEADS OPTION (4 PLCS)
0° – 15°
0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS
0.405 (10.287) MAX
0.005 (0.127) MIN 0.015 – 0.060 (0.381 – 1.524)
8
0.014 – 0.026 (0.360 – 0.660)
0.100 (2.54) BSC
5
0.025 (0.635) RAD TYP
0.220 – 0.310 (5.588 – 7.874)
1 0.045 – 0.065 (1.143 – 1.651)
6
7
2
3
4
0.200 (5.080) MAX
0.125 3.175 MIN
J8 1298
OBSOLETE PACKAGE N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510)
0.300 – 0.325 (7.620 – 8.255)
0.045 – 0.065 (1.143 – 1.651)
0.065 (1.651) TYP
0.009 – 0.015 (0.229 – 0.381)
(
0.400* (10.160) MAX
0.130 ± 0.005 (3.302 ± 0.127)
8
7
6
5
1
2
3
4
0.255 ± 0.015* (6.477 ± 0.381)
+0.035 0.325 –0.015 +0.889 8.255 –0.381
)
0.100 (2.54) BSC
0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076)
N8 1098
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254)
0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP
0.016 – 0.050 (0.406 – 1.270)
0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
8
7
6
5
0.004 – 0.010 (0.101 – 0.254)
0.050 (1.270) BSC
0.150 – 0.157** (3.810 – 3.988)
0.228 – 0.244 (5.791 – 6.197)
SO8 1298
1
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
2
3
4
11
LT1227 UO
TYPICAL APPLICATI
S
Single Supply AC-Coupled Amplifier Noninverting
Single Supply AC-Coupled Amplifier Inverting
3.58MHz Oscillator 15V
5V
5V
4.7µF
+
+
AV =
10k
22µF
100pF
10k
2.2µF
–
3.579545MHz
+
+
VOUT
75pF
10k
+ LT1227
2N3904
510Ω ≈ 10 RS + 51Ω
BW = 14Hz to 60MHz
+
VIN
1N4148
100k
4.7µF
1k
VOUT
LT1227
10k
68pF
150k
15V
– –
220µF
510Ω VIN
AV = 11 BW = 14Hz to 60MHz
RS
+
+
51Ω
220µF
51Ω VOUT
LT1227
510Ω
51Ω
+
1227 TA09
–15V
1227 TA08
Buffer with DC Nulling Loop
CMOS Logic to Shutdown Interface
1227 TA10
Optional Offset Nulling Circuit
V+
180Ω
RNULL
180Ω
10k
3
0.1µF 3
VIN
5
+
1 LT1227
10k 2
V+
15V
10k
7
3
+ 6
LT1227 6
2
VOUT
1 LT1227
2
8
–
5
–
4
4
–15V
V–
–
10k
7
+
6 RNULL = 47k FOR VS = ±5V RNULL = 150k FOR VS = ±15V 1227 TA12
5V
1.5k
10k 2N3904 100k 0.01µF 1227 TA11
+ 100k
LT1097
– 0.01µF 1227 TA07
RELATED PARTS PART NUMBER
DESCRIPTION
COMMENTS
LT1395/LT1396/LT1397 Single/Dual/Quad 400MHz Current Feedback Amplifier
12
Linear Technology Corporation
Miniature Packages: SOT-23, MSOP-8, SSOP-16
1227fb LT/CP 1001 1.5K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 1994
