what is that diode used for

Thread Starter

luciforlove

Joined Sep 11, 2012
1

hi,all!
the diode(D1) between the second BJT'b and e,what it use for,it does influence dc and signal amplification during simulation.
thank you
 

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R!f@@

Joined Apr 2, 2009
9,918
U know u should really learn to tell more abt ur circuit before asking questions.

Secondly here we have Grand Pa's :D mostly. So I think u should put a clear screen shot. Even I can't make out beside the symbols.
 
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crutschow

Joined Mar 14, 2008
34,201
That's a real Rube Goldberg of a circuit. :rolleyes: If you tell us what it is supposed to do (and what those squares represent) we might be able to help.
 

Wendy

Joined Mar 24, 2008
23,408
I am afraid I have to agree, the schematic is missing too much information to be of much use. I move it to local after waiting almost a minute to upload (I have fiber optic). Did you draw this yourself, or where did you get it?
 

Audioguru

Joined Dec 20, 2007
11,248
The schematic is fuzzy because it was saved and posted as a fuzzy JPG file type instead of as a very clear PNG file type.
Its parts are spread out too much which makes them small.
Also the schematic is covered with chicken pox dots and tiny text all over it.
The grey background should be white.
 

ramancini8

Joined Jul 18, 2012
473
Usually, this diode protects the base-emitter junction from reverse breakdown. If you don't know why the components are on the schematic you shouldn't be on a simulator; that is like letting a chimp drive your car.
 

bertus

Joined Apr 5, 2008
22,266
Hello,

Diodes can be used for several purposes:
You can use them to rectify signals.
You can use them to isolate signals.
You can use them to switch signals.
You can use them to attenuate signals.

In the circuit given it is not clear how the diodes are used.

Bertus
 

takao21203

Joined Apr 28, 2012
3,702
Usually, this diode protects the base-emitter junction from reverse breakdown. If you don't know why the components are on the schematic you shouldn't be on a simulator; that is like letting a chimp drive your car.
It is really too much demanded trying to understand what this schematic is about. It is too small, nothing can be read properly. And what is it actually? Confused.

Diodes are used from many things: dropping voltage, creating a bias, lock out reverse voltage, rectifying...or in a radio perhaps if you fancy.
 

ErnieM

Joined Apr 24, 2011
8,377
Diodes can be used for several purposes:
You can use them to rectify signals.
You can use them to isolate signals.
You can use them to switch signals.
You can use them to attenuate signals.
Cool list, what else can we add?

You can use them to clamp signals.
You can use them as a constant current source.
You can use them as a variable capacitor.

This is fun!
 

kubeek

Joined Sep 20, 2005
5,793
If those little squares represent BJTs (which you implied), why do they have 4 terminals?
RF transitors as I recall have four terminals because of reasons unknown to me, and the values look like this operates at some high frequency, so my gues is some HF amplifier.
Also I hazard to guess that the left pin is base, bottom and top are emmiter(s) and right pin is collector.
 
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