This is a Building Block for our Quantum Experimenters. As the Red Pitaya is based on an FPGA, it enjoys high status among our Quantumopticians. Unfortunately, it has no High Voltage High Speed Low Noise output.

This is a cascaded approach using two instrumentation amplifiers. On the first sight, it mayst deem strange to have a gain of Vu = 3.162277, but by that, we can maximise the bandwidth of the overall system, because we use the maximum bandwidth for each stage. (You can increase the bandwidth further by using more stages. See also this website.)

The overall Gain using two stages is Vu = 3.162277 * 3.162277 = 9.99999.

The first stage may also add an offset voltage to get a true bipolar signal. This is selecteable with a jumper, for each channel.

• Power Supply, e.g. Leomod
• Lemo Cable, e.g. this or that.

At 1 kHz, this circuit works like a charme



And can handle some overdrive (approx. 50%)



The Slew Rate Limiting kicks in. The used INA118 offers 0.9 V/µs (@ Gain=10).
The INA849 (different pinout) offers 35 V/µs in case you need it.



Small Signal Gain is - of course - much higher ...

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