Casscode Curent source - 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 28th April 2001, 09:30 AM   #1
ppl is offline ppl  United States
diyAudio Member
 
ppl's Avatar
 
Join Date: Apr 2001
Location: Seattle, WA U.S.A.
I am using a CRD (Current limiting Diode to Bias an opamp into class a and i wish to use somthing better than a resistor in series with the diode to buffer the capacetence of the Current source and i was considering a cascode type like, as Detailed in the Burr Brown AB-007 Note. Has any one done this and what results did you get. I would like to keep the Drop-out Voltage of the curent source as low as i can since the Amp is battery operated. TIA.
  Reply With Quote
Old 30th April 2001, 05:17 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Are you trying to isolate the active gain stages
from the current source's capacitance per se, or
are you trying to make the current source more
constant?
  Reply With Quote
Old 30th April 2001, 10:07 PM   #3
ppl is offline ppl  United States
diyAudio Member
 
ppl's Avatar
 
Join Date: Apr 2001
Location: Seattle, WA U.S.A.
Yes i am wanting to isolate the Current sources Capacitence. I am at present using a resistor to do this. Since this Current source is to just Bias the Gain-stage into Class A I think Accuracy may not be required but let me know if you think it should be.
  Reply With Quote
Old 1st May 2001, 04:30 PM   #4
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
It's up to you whether you want to do it or not.
I'm sure it will work fine, but the DC drop across
the resistor will tend to limit its range, so you
will want to keep that fairly low, say a couple
of volts.
  Reply With Quote
Old 2nd May 2001, 06:11 AM   #5
ppl is offline ppl  United States
diyAudio Member
 
ppl's Avatar
 
Join Date: Apr 2001
Location: Seattle, WA U.S.A.
Thank you for your reply. I am using a 1k resistor in series with a 1N5298 Current regulator Diode to Supply about 1.0 Ma of constant Current into the Opamp's output stage. The Opamp is driving the Input of a Open loop Buffer.My concern is that at large AC Voltage swings the CRD will drop out and Thus create more Distortion that the Class A Biasing would eliminate. So far the CRD and a 1K resistor works right up to the point of Clipping.I am also concerned that 1K may not be large enough to isolate the Capacitence.

This is why i am considering a casscode aproch to the Problem since this Topology has low Capacitence to start with and the Capacitence is more or less Constant with changing Voltage. TIA PPL
  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
best prices for fostex thats curent.thanx roystr Full Range 2 20th January 2005 08:08 PM
regulation of 78XX and 79XX at low curent Jim Mullally Parts 4 3rd June 2004 11:08 PM
Just an idea for a new I/V stage: what about curent mirors? Bricolo Digital Source 2 8th April 2004 09:51 AM


New To Site? Need Help?

All times are GMT. The time now is 07:01 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