Below is a diff amp I am planning to use to read value from a capacitor. I will be using a saw tooth reference voltage and output will be high when vref>Vin else low. Problem is my input voltage is negative dc voltage. Can you suggest me how to change my circuit?
Code PHP - [expand]
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.param
+ Lch = 500n
+ Wnsa = 300n
+ Wpsa = 300n
* Differential Amplifier to cleanup the output clock
You have not given any parametres, is your negative voltage -.01 or -200V?. If the negative voltage is not too high, just feed it via two high value resistors to a positive voltage and use the join between them as your comparison point. e.g. input = -.5V feed via a 1M and another 10 M to +5V would give the new input as 0V, feed via 4.5 M from +5V and the point becomes +.5V.
Frank