Due to my - in the highest sensitive ranges - a little bit noisy Rigol DS-1054z scope, I decided to provide a small pre-amplifier for low-voltage measurements (a.k.a. electret microphone signals, shunt-voltages, etc.). For best performance in the micro-volt range, a dual stage amplifier (both stages provide 10V/1V gain) is built with the MCP6V27. A third and last stage gives the final 10V/1V amplification resulting in a gain of 1000V/1V with a 3db cut-off at ~200 kHz.
For the third stage and the virtual ground a cheaper MCP6292 is used.
The input voltage must not exceed ±1.5V!
Current consumption should be ~1.6mA, the CR2032 coin-cell should last about 200h. The slide-switch disables the op-amps, if 1V/1V is selected.
Further improvements:
- TVS-Diodes for clamping input voltage?
| Ref | QTY | Value | Mouser |
|---|---|---|---|
| BT1 | 1 | Keystone 1058 | Keystone 1058 |
| C1, C2, C3 | 3 | 22pF | 885012007002 |
| C4, C5 | 2 | 100nF | C0805C104K5RACTU |
| J1, J2 | 2 | Conn_Coaxial | TE-5-1634503-1 |
| R1, R7, R12 | 3 | 1k | RR1220P-102-D |
| R2, R8, R13 | 3 | 6k8 | RR1220P-682-D |
| R3, R9, R14 | 3 | 2k2 | RR1220P-222-D |
| R6, R5 | 2 | 100k | RR1220P-104-D |
| R11, R4, R10, R15 | 4 | 270R | RC0805JR-07270RL |
| SW1 | 1 | SS-24E06-TG 5 (P) | SS-24E06-TG 5 (P) |
| U1 | 1 | MCP6V27-E/SN | MCP6V27-E/SN |
| U2 | 1 | MCP6292-E/SN | MCP6292-E/SN |
Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) 2018 Wolfgang Jung, Ideas In Logic - Jung & Kesten GbR