# Effect of changing current sense resistor value in amplifier circuit

I am trying to implement a current output amplifier circuit shown below. Current is measured across sense resistor Rs to adjust input voltage Vin.

Gain: G = -Iout/Vin = R2/(Gain-of-IA1*R1*RS)

The gain of this circuit is set at 1 with R2 = 1kohm, R1 = 100kohm, RS = 0.01ohm, RL is the load. It has an instrumentation amplifier IA1 on the feedback path for less noise and better resolution. The gain of IA1 is also 1. If I decide to increase resistance of Rs and decrease resistance of R1 while keeping the gain at 1. How would changing sense resistor value affect my system performance?

$$\ \frac{- I_{out}}{V_{in}} = \frac{R_2}{R_1*IA1*R_S}\$$
• @Linh, by changing R1, input impedance will be change. if you change Rs, you should aware of power dissipation, $P_d = R_s * i^2$, – M KS Nov 19 '18 at 11:11