# Analyse these circuits

#### ediakpan

Joined Sep 12, 2018
5

#### AnalogKid

Joined Aug 1, 2013
9,296
You first. What do you think each one does? What is the overall function of the circuits when combined? In other words, what is this thing?

ak

#### KeithWalker

Joined Jul 10, 2017
1,858
There is no information attached. What exactly do you want analysing?

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#### ericgibbs

Joined Jan 29, 2010
13,278
hi,
I see that you are student, is this a homework assignment.?
E

#### ediakpan

Joined Sep 12, 2018
5
You first. What do you think each one does? What is the overall function of the circuits when combined? In other words, what is this thing?

ak
am working on an FM transmitter, those are the circuit diagrams

#### ediakpan

Joined Sep 12, 2018
5
There is no information attached. What exactly do yo want analysing?
its an fm transmitter circuit

#### ediakpan

Joined Sep 12, 2018
5
hi,
I see that you are student, is this a homework assignment.?
E
its a fm transmitter project am working on

Mod: OK, thank you.

Last edited by a moderator:

#### ediakpan

Joined Sep 12, 2018
5
Looks like some sort of a metal detector or a proximity detector...proximity to what, though?
its an fm transmitter circuit

#### AnalogKid

Joined Aug 1, 2013
9,296
If you are working on it, and this is your design, tell us how you think it works and we will review your description. For example, what do L3 and L4 do? What are the DC operating points of Q3 and Q5?

Also, there is an 18-pin device with no reference designation, part number or any other information. What is it?

ak

#### OBW0549

Joined Mar 2, 2015
3,566
Analyze these circuits
ANALYSIS:

1. Audio Preamplifier: probably will work. Not saying how well it will work, but it should do something recognizable.

2. RF Output Stage: None of the transistors has any means of DC bias, and will never turn on. This part of the circuit is TOTALLY boned.

3. Big Diagram on Bottom: No identifying info on that 18-pin IC on the lower right, so it's anybody's guess. The three pushbutton switches do nothing, as Q4 has no means of turning on. As for the microcontroller and the two displays, who knows.

SUMMARY: This design needs work.

#### Audioguru

Joined Dec 20, 2007
11,249
I commented about it on another website forum.

#### AnalogKid

Joined Aug 1, 2013
9,296
3. Big Diagram on Bottom: No identifying info on that 18-pin IC on the lower right, so it's anybody's guess.
One side of the crystal and three signal pins are grounded.

ak

#### OBW0549

Joined Mar 2, 2015
3,566
One side of the crystal and three signal pins are grounded.
Good catch. I don't think this circuit is going to be transmitting anything anytime soon...