40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
Entry  Sat Mar 4 17:01:00 2017, yinzi, DailyProgress, TempCtrl, npn transistor buffer and metal piece measurements 6x
    Reply  Thu Mar 9 15:02:46 2017, awade, DailyProgress, TempCtrl, npn transistor buffer and metal piece measurements 
Message ID: 1824     Entry time: Thu Mar 9 15:02:46 2017     In reply to: 1822
Author: awade 
Type: DailyProgress 
Category: TempCtrl 
Subject: npn transistor buffer and metal piece measurements 

What exactly is the offset? Is there some threshold voltage the BJT requires before it starts conducting, maybe one should expect a ~0.7 V difference between the op-amp output and the load voltage? There should be some opamp configuration where can you can bias the feed back to the -ve pin of the op-amp: this is commonly done for op amps running with single sided supply.

Is it possible to make use fo the full +/- 15 V range? 

Also, want to use a FET on the output BJT, it has lower noise and better thermal stability. 

 

Quote:

So I put together a little test circuit to test out a NPN BJT buffer circuit with a TIP122 transistor and an OP27 op amp. Power voltages are ~ +-14V, just used the positive rail as V+ for the transistor.

 

 

ELOG V3.1.3-