Resistor ratio question for differential amplifier

[jg001]

Hello,

I need to build a differential amplifier with a gain > 1. I know that the gain is equal to R_feedback / R_input (when resistors on the other leg are the same as this leg).

Let's say I need a gain of 10. So, I can use many sets of resistor-pairs: 10 ohm / 1 ohm, 10K/1K, 100K/10K etc. The gain will be the same. But something tells me that the performance may not be the same.

So what criteria should I use when picking my resistor values? Thanks in advance for any response.

 

[shahbaz.ele]

try to work out your current requirements then choose the resistor values.
use any pair according to your current requirement.

 

[LvW]

Hello,

I need to build a differential amplifier with a gain > 1. I know that the gain is equal to R_feedback / R_input (when resistors on the other leg are the same as this leg).

What kind of diff. amp are you speaking of (opamp or lumped?).

---------- Post added at 09:37 ---------- Previous post was at 09:23 ----------

OK, from your description it looks like an opamp circuit.
General rule: Resistors should be large if compared with the opamp open-loop output impedance (50...100 ohms) and at the same time small if compared with the opamp input impedances (1...5 Mohms).
Normally, this results in resistors within the kohm range (1k...100k max).