PNP Differential Amplifier

Thread Starter

Darkcat

Joined Apr 16, 2013
2
It has been quite a while since I have had to deal with BJTs and have no clue where to even start :confused: I have to use PNP transistors to create a single-ended inverting output, differential amplifier.

Collector Resistance = Load Resistance = 1.5K Ohms
Current Value = 4.5mA

This is about all I know about this project :\ Any help, even a basic understanding of how PNPs work, would be very much appreciated.
 

takao21203

Joined Apr 28, 2012
3,702
Interestingly many NPN circuits can be changed to use PNP instead.

The gate or here base voltage is negative. Current flows out of the base.
 

crutschow

Joined Mar 14, 2008
34,285
Generally you can take an NPN circuit, substitute PNP's for the NPN's and reverse the polarity of all voltage sources.

Is there any gain or voltage output requirements for this amp?
 

WBahn

Joined Mar 31, 2012
29,979
It has been quite a while since I have had to deal with BJTs and have no clue where to even start :confused: I have to use PNP transistors to create a single-ended inverting output, differential amplifier.

Collector Resistance = Load Resistance = 1.5K Ohms
Current Value = 4.5mA

This is about all I know about this project :\ Any help, even a basic understanding of how PNPs work, would be very much appreciated.
If you have "no clue where to even start" and need help with "even a basic understanding of how PNPs work", then it sounds like the place to start is by retaking the prerequisite course(s) for the one you are in. If this is truly an accurate statement of your level of preparedness, the proceeding on will just lead you further down a hole until you are trapped in a place where you just flounder around aimlessly. The sooner you address these difficiencies, the better.
 

Thread Starter

Darkcat

Joined Apr 16, 2013
2
If you have "no clue where to even start" and need help with "even a basic understanding of how PNPs work", then it sounds like the place to start is by retaking the prerequisite course(s) for the one you are in. If this is truly an accurate statement of your level of preparedness, the proceeding on will just lead you further down a hole until you are trapped in a place where you just flounder around aimlessly. The sooner you address these difficiencies, the better.
Perhaps "no clue where to start" is not an accurate statement. I can identify a PNP, as well as, the collector, emitter, & base tail. I remember the voltage difference required to make sure it is in ACTIVE mode. Creating a current mirror with NPNs is also something I recall. What escapes me is how to create a differential amplifier with PNPs. It is quite easy to forget certain things when not used often.
 

WBahn

Joined Mar 31, 2012
29,979
Do you recall how to make a differential pair using NPNs? If so, work the problem as though that was what you were asked to do. Then worry about flipping everything later. You need to start from something you remember how to do and work your way forward.
 
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