Small low power beginner amp

Tekko · 25th January 2011, 11:49 AM

Heres a true beginner circuit:

http://i.imgur.com/yLaRn.jpg

And no its not two transistors, its darlingtons like MJE703/803 or TIP142/147.

The two resistors sets the bias current, around 10-20mA is a good starting point, above that you need a bias compensation circuit.

Nico Ras · 25th January 2011, 06:56 PM

So where is the image that we are looking for.

Tekko · 25th January 2011, 07:02 PM

Here:

http://i.imgur.com/aI0Gx.jpg

But it needs a cap in series with input and feedback.

jaycee · 25th January 2011, 07:56 PM

Yes the important part is you must make the opamp drive a constant load... then the output transistors follow the current being drawn by the opamp. Of course this only works with single opamps.

You might be surprised to find that this idea is actually used a fair bit, more refined than what you show here, but the same principle never the less. Usually it involves current mirrors which then drive the later stages, but the principle is the same.

Tekko · 25th January 2011, 08:41 PM

Like this:

http://i.imgur.com/ZFtQA.jpg

jaycee · 25th January 2011, 09:01 PM

If you want to explore this further, look at the Alexander amp, its an Analog Devices app note AN-211.

25th January 2011, 11:49 AM	#1
Tekko diyAudio Member Join Date: Jan 2005	Small low power beginner amp Heres a true beginner circuit: http://i.imgur.com/yLaRn.jpg And no its not two transistors, its darlingtons like MJE703/803 or TIP142/147. The two resistors sets the bias current, around 10-20mA is a good starting point, above that you need a bias compensation circuit.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Small low power amplifier to put inside guitar	loffe	Solid State	0	19th February 2010 12:00 PM
TK2050 power switch advice needed from amp DIY beginner	westsounds	Class D	0	29th December 2009 12:35 PM
Some beginner questions about B3 preamp and F4 power amp	njepitt	Pass Labs	32	28th June 2009 09:55 PM
Small beginner amplifier and hello :)	MadsKaizer	Tubes / Valves	15	20th April 2009 10:38 PM
Suggestions for beginner Power Amp design	spasmolytic	Pass Labs	6	6th February 2004 02:43 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

25th January 2011, 06:56 PM	#2
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	So where is the image that we are looking for.

25th January 2011, 07:02 PM	#3
Tekko diyAudio Member Join Date: Jan 2005	Here: http://i.imgur.com/aI0Gx.jpg But it needs a cap in series with input and feedback.

25th January 2011, 07:56 PM	#4
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Yes the important part is you must make the opamp drive a constant load... then the output transistors follow the current being drawn by the opamp. Of course this only works with single opamps. You might be surprised to find that this idea is actually used a fair bit, more refined than what you show here, but the same principle never the less. Usually it involves current mirrors which then drive the later stages, but the principle is the same.

25th January 2011, 08:41 PM	#5
Tekko diyAudio Member Join Date: Jan 2005	Like this: http://i.imgur.com/ZFtQA.jpg

25th January 2011, 09:01 PM	#6
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	If you want to explore this further, look at the Alexander amp, its an Analog Devices app note AN-211.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)