271 Tiny Opamp
271 : Tiny Opamp
- Author: argunda
- Description: Super simple two stage opamp without miller compensation
- GitHub repository
- Clock: 0 Hz
- Feedback: 🟡 1
How it works
This opamp has VDD=1.8V and VSS=0V. It's input common mode range is not very good so make sure your AC input signal is centered around 0.9V. The opamp is internally biased so you just need to apply a differential input.
It should be able to hit 60dB gain at low frequencies. Please do not connects loads requiring more than a few mA.
How to test
Power up the chip, test opamp in closed loop configuration only. VOUT is analog pin 0. PLUS is a differential input on analog pin 1. MINUS is a differential input on analog pin 2.
External hardware
At the bare minimum a resistor at the output is needed to test the opamp as a source-follower. Use multimeter or oscilloscope to probe the output.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | pause | blue | |
| 1 | new_game | green | |
| 2 | down_key | red | |
| 3 | up_key | hsync | |
| 4 | vsync | ||
| 5 | speaker | ||
| 6 | col0 | ||
| 7 | row0 |
Analog pins
ua | PCB Pin | Internal index | Description |
|---|---|---|---|
| 0 | B5 | 11 | VOUT1 |
| 1 | B0 | 6 | PLUS1 |
| 2 | B4 | 10 | MINUS1 |
| 3 | B1 | 7 | VOUT2 |
| 4 | B3 | 9 | PLUS2 |
| 5 | B2 | 8 | MINUS2 |
User feedback
- smunaut: Tested first op-amp only, in a unity inverted config ( minus wired to vout ). Seems it self oscillates a bit, but otherwise, it acts as a op-amp mostly.