See any problems with the circuit below? The intent is to buffer Vin somewhat, while protecting the following ADC from voltages that go above
4.7V or below 0.3V. The idea is that while the LM358 can't pull its output above 3V or so, R1 will -- limited by R3. On the low-voltage side, R2 and R3 will only allow the output to be pulled most of the way to 0V, but not all. The whole assembly should have a reasonably low output impedance, except for the inevitable weirdness of being able to pull down a lot better than it can pull up.Comments welcome.
+5V + | | +5V .-. + | | R1 | | | 1K LM358 | R2 '-' Vin |\| 64.9 | o------------|+\ ___ | | >----|___|-----o .-----|-/ | Vout | |/| o------o----------o | | | | | | .-. | | === R3 | | | | GND 15.8K | | | | '-' | | | | | | | | R4 === | | 100 GND | | ___ | '-----|___|--------------------' (created by AACircuit v1.28.6 beta 04/19/05