Transistor Amplifier Problem

Thread Starter

Zeeus

Joined Apr 17, 2019
523
made this but having little problem.. The voltages check out except the voltage at the collector of Q3 which TS wants it to be 5v but getting about 0.9v

Like, it's working on spice but not real

Please what's problem?

In real, there's a 22uf across Vcc

Also, any one that uses the spice : see what happens if the input signal is connected and 2.6nf (tried others on spice) is connected at base of Q3

Thanks thanks
 

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ericgibbs

Joined Jan 29, 2010
9,852
hi,
Using a1uV input signal at 1kHz is totally unrealistic, what is the expected input signal level in normal use.?
E

Update:
Look at the LM386 Gain plot.
AAA 221 18.28.gif
 

Thread Starter

Zeeus

Joined Apr 17, 2019
523
hi,
Using a1uV input signal at 1kHz is totally unrealistic, what is the expected input signal level in normal use.?
E
dunno oo...How can measure it? The input signal is from an antenna
Just used 1uv to calculate the gain (Approx)
 

Thread Starter

Zeeus

Joined Apr 17, 2019
523
hi,
The LM386 is an audio amplifier, what signals from an antenna do you expect to amplify.?
Frequency range..?
E
7mhz...through a bandpass filter then mixer to produce audio frequency
But why is the collector dc voltage 5V on spice but not so in real (checked board but looks like no bad connection)
 
Last edited:

ericgibbs

Joined Jan 29, 2010
9,852
hi,
As I said, in the real world your preamp is unstable, so it could appear to be saturated at the output.
Use a Scope to measure the Q3 collector voltage.

E
 

ericgibbs

Joined Jan 29, 2010
9,852
hi,
Do you have a good quality photo of the project showing the components that you could post.?
The LTSpice sim shows that the amp design has a problem.
E
 

Thread Starter

Zeeus

Joined Apr 17, 2019
523
hi,
Do you have a good quality photo of the project showing the components that you could post.?
The LTSpice sim shows that the amp design has a problem.
E
Sorry, late reply..no really good photo to show the amp...its copper clad board
guess have seen problem
 

ericgibbs

Joined Jan 29, 2010
9,852
hi,
I would suggest you work out what the signal voltage range will be on the input of the amplifier, then you can design the amp to suit the LM386.
E
 

MisterBill2

Joined Jan 23, 2018
5,802
made this but having little problem.. The voltages check out except the voltage at the collector of Q3 which TS wants it to be 5v but getting about 0.9v

Like, it's working on spice but not real

Please what's problem?

In real, there's a 22uf across Vcc

Also, any one that uses the spice : see what happens if the input signal is connected and 2.6nf (tried others on spice) is connected at base of Q3

Thanks thanks
The circuit is a 3 stage DC coupled amplifier, with DC feedback. And if it is running on a simulator then there is an entry error.
 
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