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Choosing components

U1A and U1B must be low-noise opamps that have a low offset voltage. We need a low-noise opamp, because the input signal is devided by 100 by R1 and R3. So the input voltage at U1A is just a few mV. A low offset voltage is needed because of the high gain. A generic cheap opamp will carry a large DC component at its output. This DC voltage will also be amplified by U1B. A NE5532 perfect for this job. If we want to use a cheap opamp anyway (for example a TL082), we will have to add a 100n capacitor between node pin 1/C2 and pin 5, and a 1MΩ resistor between pin 5 and ground. This will block the DC component without attenuating the low-frequency signals too much.

U2 can be any generic opamp. A TL081 works perfectly.

JFET T1 is not very critical, as long as its pinch-off voltage isn't too low. A BF245A (pinch-off voltage: -1.5V) is a good choise. If we only have a BF245C (pinch-off voltage: -4.5V), then we can use it as well. We'll just turn up U2's gain using P1.

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