single transistor audio amp - Electronic Circuits Projects Diagrams Free

mamun2a · 12th December 2006, 08:21 AM

I Need a single transistor base economic mini audio amp.

Gayan Soyza · 12th December 2006, 09:05 AM

Quote:

Originally Posted by mamun2a

I Need a single transistor base economic mini audio amp.

Why do u bothering with small transistor amps......for learning purposes like transistor biasing its good.......there are plenty economic audio IC's designed for mini audio...

You mentioned one transistor amplifier only give u power output about 0.5w..without going to a bigger transistor...or may be u asking a single transistor amplifier to reduce the space in the cct...

there are IC's designed from 5pin SIL,8pin DIPS .....giving a nice smooth outputs..having only few external parts.....& need only a small voltage & current.like KA 2209,TDA 2002....etc

Hero999 · 12th December 2006, 05:39 PM

Is this college work?

Do it yourself.

mamun2a · 13th December 2006, 03:34 AM

ya not actually, amplify with least parts

kchriste · 13th December 2006, 04:12 AM

Quote:

amplify with least parts

Then an IC (Which is one part) is the best route.
You don't mention how much gain or the output power level that you need. We need this info to give you a valid answer.

Sceadwian · 13th December 2006, 04:13 AM

Then find an audio amplifier IC. A low power amplifier IC might have a couple decoupling capactors and a resistor or two. A single transistor amplifier could have a dozen or more supporting components.

k7elp60 · 13th December 2006, 04:28 AM

It is possible to use a N channel power mosfet, connect the 4 ohm or 8 ohm speaker right between the drain and the + power supply lead. Biasing the gate to class A operation you could get some power out that way and it would be pretty sensitive.

Hero999 · 13th December 2006, 01:10 PM

That was my first audio amp and it was crap, the distortion was terrible and there was DC in the speaker so it got hot.

Anyway you haven't given any information.

Gain?

Power?

The attached schematic is a the simplist audio amp you can build.

audioguru · 13th December 2006, 02:58 PM

Hi Hero,
I simulated your small amplifier.
1) With an 8 ohm speaker, it doesn't have gain, it has loss.
2) It has a very small output power, a whopping 0.8mW. Headphones have much more power.
3) It is distorted.

I also tried it as an emitter-follower and its loss is less. Its output power is 0.2mW.

Hero999 · 13th December 2006, 03:23 PM

Of course it won't power an 8

hm: speaker (I'm insulted you would ever think that I'm so much of a noob that I didn't know it won't do that!) but where did he ever say he wanted to do that?

He just said he wanted an audio amplifier and this circuit will do just that.

He didn't say what gain he required, so I just designed one with a gain of 4.7.

I was proving a point, if you make a vague request then no one wil be able to give you what you want.

**Nigel Goodwin** · 13th December 2006, 03:29 PM

Quote:

Originally Posted by Hero999

He didn't say what gain he required, so I just designed one with a gain of 4.7.

It's a bit hopeful!, it's not an opamp - you can't hope for accurate gain setting in that way.

Hero999 · 13th December 2006, 03:37 PM

Alright then with a transistor Hfe of 100 the gain will be 4.489, an error of only 4.489%!

**Nigel Goodwin** · 13th December 2006, 05:24 PM

Quote:

Originally Posted by Hero999

Alright then with a transistor Hfe of 100 the gain will be 4.489, an error of only 4.489%!

Will it be that close?.

audioguru · 13th December 2006, 06:13 PM

My sim of the single transistor amplifier without a load shows a voltage gain of only 3.35.

Hero999 · 13th December 2006, 08:06 PM

Why so low?

The simulation must be wrong, either that or the transistor model you used has a gain of a lot less than 100.

$A_C = \frac{A_O}{1+ \beta A_O}$
$\beta = \frac{R_I}{R_F}$
Therefore:
$\beta = \frac{47}{10}=0.213$
$A_O = 100$
$A_C=\frac{100}{1+0.213 \times 100}=4.489$

Or have I got my sums wrong?

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12th December 2006, 08:21 AM	(permalink)
mamun2a	single transistor audio amp I Need a single transistor base economic mini audio amp. __________________ 'if u cant beat him then join him' I always say...

12th December 2006, 05:39 PM	(permalink)
Hero999	Is this college work? Do it yourself. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

13th December 2006, 03:34 AM	(permalink)
mamun2a	ya not actually, amplify with least parts __________________ 'if u cant beat him then join him' I always say...

13th December 2006, 04:13 AM	(permalink)
Sceadwian	Then find an audio amplifier IC. A low power amplifier IC might have a couple decoupling capactors and a resistor or two. A single transistor amplifier could have a dozen or more supporting components. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

13th December 2006, 04:28 AM	(permalink)
k7elp60	It is possible to use a N channel power mosfet, connect the 4 ohm or 8 ohm speaker right between the drain and the + power supply lead. Biasing the gate to class A operation you could get some power out that way and it would be pretty sensitive. __________________ The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best. Show me a different way. I have an open mind.

13th December 2006, 03:23 PM	(permalink)
Hero999	Of course it won't power an 8hm: speaker (I'm insulted you would ever think that I'm so much of a noob that I didn't know it won't do that!) but where did he ever say he wanted to do that? He just said he wanted an audio amplifier and this circuit will do just that. He didn't say what gain he required, so I just designed one with a gain of 4.7. I was proving a point, if you make a vague request then no one wil be able to give you what you want. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

13th December 2006, 03:37 PM	(permalink)
Hero999	Alright then with a transistor Hfe of 100 the gain will be 4.489, an error of only 4.489%! __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

13th December 2006, 08:06 PM	(permalink)
Hero999	Why so low? The simulation must be wrong, either that or the transistor model you used has a gain of a lot less than 100. $A_C = \frac{A_O}{1+ \beta A_O}$ $\beta = \frac{R_I}{R_F}$ Therefore: $\beta = \frac{47}{10}=0.213$ $A_O = 100$ $A_C=\frac{100}{1+0.213 \times 100}=4.489$ Or have I got my sums wrong? __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.