High voltage OPAMP / PREAMP - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th February 2002, 09:31 PM   #1
diyAudio Member
 
Join Date: Jan 2002
Location: Williamsport, PA
Send a message via AIM to hugeli60
Default High voltage OPAMP / PREAMP

I am working on a high voltage opamp for the pre-amp to a MOSFET voltage follower. What do you guys think about this schematic?

I am planning on using SOT-223 ZETEX HIGH Voltage Devices for the diff amp stage and there High current devices in the output stage.

I want this thing to operate at +/-100v and drive a mosfet power follower. Caps are TBD values. I dont have a good spice program yet to simulate.
Attached Images
File Type: gif opamp.gif (10.3 KB, 600 views)
  Reply With Quote
Old 15th February 2002, 09:00 AM   #2
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Your currentmirror Q1 and Q2 need a connection from their base to Q1 collector.
Place a bias resistor over C9.

Try find BJT with a high "va" and run them at ~.5 - 1 mA.
FZX493 and FZX593 is a good device from Zetex.

The spice data says :

NF = .99
Va = 270

Sonny
  Reply With Quote
Old 15th February 2002, 11:08 AM   #3
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Now i have a little more time.

You do know that C1 does not have a function?.

Why do you have installed C2,C3,C4,C6,C7??? They are not necessary. C5 (compensation cap) is enough to control the opamp's freq. response/phase margin.

Sonny
  Reply With Quote
Old 15th February 2002, 11:51 AM   #4
yeti is offline yeti  Germany
diyAudio Member
 
Join Date: Nov 2001
Location: Ewersbach
Default Preamp

The 4 output Transistors will blow, the current mirror Q1,Q2 will need biasing.

Regards:

Arne
  Reply With Quote
Old 15th February 2002, 03:44 PM   #5
diyAudio Member
 
Join Date: Jan 2002
Location: Williamsport, PA
Send a message via AIM to hugeli60
OOPS. I sent the old schematic. The base connection of the current mirrors should be there. I wanted to put spaces where I could put capacitors or other components to play with the circuit.


I Am not sure what output devices to use yet. I need to find something beefy.Thanks for the input
  Reply With Quote
Old 15th February 2002, 05:28 PM   #6
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I doubt that you need this much output stage just
to drive the inputs of MOSFET followers. Maybe
you should dump the outputs and just use the drivers.
  Reply With Quote
Old 16th February 2002, 03:05 AM   #7
diyAudio Member
 
Join Date: Jan 2002
Location: Williamsport, PA
Send a message via AIM to hugeli60
I just wanted to make sure I have enough kick for large banks of MOSFETS.
  Reply With Quote
Old 17th February 2002, 08:03 PM   #8
diyAudio Member
 
Join Date: Feb 2002
Location: Belgium
For a free spice version: http://www.winspice.com/
No schematic entry, but fast.

Suggestions:
- 2 small resistors (50-300 Ohm) in series with the emitors of the curent mirror Q1 Q2
- 2 even smaller resistors (10-30 Ohm) in series with the input pairs emitor Q4 Q5
- use leds to bias the current sources, zeners can be very noisy
- take a look at transistors meant for video stages, plenty of gain and voltage.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
High voltage Opamp with power transistors sivan_and Solid State 13 1st January 2009 10:42 AM
High DC offset voltage at preamp output mmerig Solid State 18 23rd May 2008 07:44 AM
Preamp PS has too high a voltage- insert R? lgreen Solid State 16 22nd July 2007 07:04 PM
high voltage input opamp sunrise Chip Amps 7 9th April 2007 06:54 PM


New To Site? Need Help?

All times are GMT. The time now is 09:38 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2