Controlled Input Impedance for Op-Amp Circuit

Other Hardware General Electronics
1

Hi,

I want to control the input impedance to 1 kΩ at the input of an op-amp circuit. I have five op-amp configurations:

  1. Voltage Follower
  2. Non-Inverting
  3. Inverting
  4. Differential Op-Amp
  5. Instrumentation Op-Amp

Can anyone help me with this?

2

Here is a voltage follower with 1K input impedance:

Capture
Capture421×347 8.3 KB

Similar approaches would work for the other cases.

1 Like
3

With correct feedback the opamp inputs have the same voltage. The in- voltage typically is controlled by the output-input-GND voltage divider. Lay out that divider for the intended amplification.

Now consider which voltage difference will result from some circuit input voltage change, and how it is reflected on the in+ and in- pins. Compute the input resistor between circuit and opamp inputs to reflect your intended input impedance.