Datasheet LT1189 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Low Power Video Difference Amplifier |
| Pages / Page | 12 / 10 — APPLICATI. S I FOR ATIO. Closed-Loop Voltage Gain vs Frequency. Reducing … |
| File Format / Size | PDF / 318 Kb |
| Document Language | English |
APPLICATI. S I FOR ATIO. Closed-Loop Voltage Gain vs Frequency. Reducing the Closed-Loop Bandwidth
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LT1189
O U U W U APPLICATI S I FOR ATIO Closed-Loop Voltage Gain vs Frequency Reducing the Closed-Loop Bandwidth
30 Although it is possible to reduce the closed-loop band- CFB = 0pF width by using a feedback zero, instability can occur if the 20 bandwidth is made too low. An alternate technique is to do differential filtering at the input of the amplifier. This 10 CFB = 5pF technique filters the differential input signal, and the differential noise, but does not filter common-mode noise. 0 VS = ±5V Common-mode noise is rejected by the LT1189’s CMRR. TA = 25°C –10 AV = 4 CLOSED-LOOP VOLTAGE GAIN (dB) RFB = 900Ω
10MHz Bandwidth Limited Amplifier
RG = 300Ω –20 100k 1M 10M 100M R1 FREQUENCY (Hz) 5V 110Ω 3 LT1189 • AI06 + 7 2 SIG – C1 6
Small-Signal Transient Response
LT1189 68pF 1 VOUT REF eND 8 FB 4 –5V 909 R2 Ω eNCM 110Ω AV = 10 100Ω 1 f–3dB = 2π(R1 + R2)C1 SIG + eN eN V D CM OUT = + FILTER CMR LT1189 • AI09
Using the Shutdown Feature
The LT1189 has a unique feature that allows the amplifier AV = 4, RFB = 910Ω, RG = 300Ω to be shutdown for conserving power, or for multiplexing LT1189 • AI07 several amplifiers onto a common cable. The amplifier will
Small-Signal Transient Response
shutdown by taking pin 5 to V–. In shutdown, the amplifier dissipates 15mW while maintaining a true high impedance output state of about 20kΩ in parallel with the feedback resistors. For MUX applications, the amplifiers may be configured inverting, non-inverting, or differential. When the output is loaded with as little as 1kΩ from the amplifier’s feedback resistors, the amplifier shuts off in 600ns. This shutoff can be under the control of HC CMOS operating between 0V and – 5V. AV = 4, RFB = 910Ω, RG = 300Ω, CFB = 5pF LT1189 • AI08 10
O U U W U APPLICATI S I FOR ATIO Closed-Loop Voltage Gain vs Frequency Reducing the Closed-Loop Bandwidth
30 Although it is possible to reduce the closed-loop band- CFB = 0pF width by using a feedback zero, instability can occur if the 20 bandwidth is made too low. An alternate technique is to do differential filtering at the input of the amplifier. This 10 CFB = 5pF technique filters the differential input signal, and the differential noise, but does not filter common-mode noise. 0 VS = ±5V Common-mode noise is rejected by the LT1189’s CMRR. TA = 25°C –10 AV = 4 CLOSED-LOOP VOLTAGE GAIN (dB) RFB = 900Ω
10MHz Bandwidth Limited Amplifier
RG = 300Ω –20 100k 1M 10M 100M R1 FREQUENCY (Hz) 5V 110Ω 3 LT1189 • AI06 + 7 2 SIG – C1 6
Small-Signal Transient Response
LT1189 68pF 1 VOUT REF eND 8 FB 4 –5V 909 R2 Ω eNCM 110Ω AV = 10 100Ω 1 f–3dB = 2π(R1 + R2)C1 SIG + eN eN V D CM OUT = + FILTER CMR LT1189 • AI09
Using the Shutdown Feature
The LT1189 has a unique feature that allows the amplifier AV = 4, RFB = 910Ω, RG = 300Ω to be shutdown for conserving power, or for multiplexing LT1189 • AI07 several amplifiers onto a common cable. The amplifier will
Small-Signal Transient Response
shutdown by taking pin 5 to V–. In shutdown, the amplifier dissipates 15mW while maintaining a true high impedance output state of about 20kΩ in parallel with the feedback resistors. For MUX applications, the amplifiers may be configured inverting, non-inverting, or differential. When the output is loaded with as little as 1kΩ from the amplifier’s feedback resistors, the amplifier shuts off in 600ns. This shutoff can be under the control of HC CMOS operating between 0V and – 5V. AV = 4, RFB = 910Ω, RG = 300Ω, CFB = 5pF LT1189 • AI08 10
