+Vin and -Vin

Thread Starter

new2circuits

Joined Apr 22, 2009
21
HI: Can someone explain the whole +Vin and -Vin concept as it relates to a differential input to an op amp for instance or any device that accepts a dual supply?
Thanks
 

Audioguru

Joined Dec 20, 2007
11,248
If an opamp or comparator has a positive and negative supply then the input and the output can be at 0VDC and the signal will swing positive and negative without coupling capacitors.
 
A differential input circuit is one that actively responds to the difference between two terminals rather than the difference between one terminal and ground.

The +Vin and -Vin are defined as the differential inputs of the op amp. The output of an op amp is the gain, A, multiplied by the difference of +Vin and -Vin.

Output = A * ((+Vin) - (-Vin))

In the case of an op amp the gain A is usually very high and therefore feedback is placed around the op amp to control it.

The differential inputs are independent of whether or not the device accepts a dual supply. The idea of dual supply is explained in #2 by Audioguru.
 

Thread Starter

new2circuits

Joined Apr 22, 2009
21
Thanks to both of you for your response. I appreciate it.

Looks like I need to go back to basics and understand the concept of dual supply and +Vin -Vin a bit more. I studied ee a long time ago, but never really used it until now. I'm finding it difficult to come back up to speed, so I appreciate you getting me there via your answers. Thanks
 
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