I need to design a "front end" that will connect a power sensing diode to some other measurement instrumentation. The gain should be abour x2500, the input signal will be of the order of 1mV I need to be able to vary the input impedance from 100 ohms to a few kOhm by changing components low-drift since it will be part of a stabilisation circuit The PCB desing should be able to handle bandwidths of between 100 Hz to 10kHz, depending on component values Reasonably low noise The complete circuit also needs to have offset adjustment Cost is not an issue (this is for work, and my time is much more expensive than the components) There is nothing "special" about this circuit and the low BW means that a single non-inverting op-amp (with resistor to ground to change the input impedance) for the gain and then second one for adjusting the offset (summing the signal with the voltage from a precision voltage reference) would in principle work since the GBW is quite low even for x2500 gain. However, I've seen a few people recommend a two-state two op-amp circuit whenever using gains as high as this, mainly because of problems with oscillations. I am aware that a cascade is sometimes used to increase the input impedance, but that is not an issue here. Hence, one alternative would be to cascade two inverting op-amps and "divide" the gain between them (say x250 in the first stage), which would also make it easy to change the input impedance. Does anyone have any practical experienc with this? Also, if using two op-amps could I use a dual op-amp such as a OPA2188 or something similar?