Why did you left out the diodes?
I build the circuit for fun, but its not doing anything.
No voltage over R22. Bias doesn't affect anything and no current is drawn into the circuit.
Pfff...
I build the circuit for fun, but its not doing anything.
No voltage over R22. Bias doesn't affect anything and no current is drawn into the circuit.
Pfff...
The diodes never normally come into play, they provide limited protection in the event of abusing the amplifier or testing using highly reactive loads at full output swing.
Two things to check first.
1/ That the output has no significant DC offset.
2/ That there is a voltage across R17 and R18, the 1.5 ohm resistors (this voltage will be less than 0.7 volts) and that this voltage varies with the bias control.
If you do have voltage across the resistors, how high does it go.
If you can't find anything obvious then copy and paste this with all the voltages filled in 🙂
Q1
E=
B=
C=
Q2
E=
B=
C
Q3
E=
B=
C=
Q4
E=
B=
C=
Q5
E=
B=
C=
Q6
E=
B=
C=
Q7
E=
B=
C=
Q8
E=
B=
C=
Q9
E=
B=
C=
Q10
E=
B=
C=
Q11
E=
B=
C=
Q12
E=
B=
C=
Q13
E=
B=
C=
Q14
E=
B=
C=
Q15
E=
B=
C=
Q16
E=
B=
C=
Two things to check first.
1/ That the output has no significant DC offset.
2/ That there is a voltage across R17 and R18, the 1.5 ohm resistors (this voltage will be less than 0.7 volts) and that this voltage varies with the bias control.
If you do have voltage across the resistors, how high does it go.
If you can't find anything obvious then copy and paste this with all the voltages filled in 🙂
Q1
E=
B=
C=
Q2
E=
B=
C
Q3
E=
B=
C=
Q4
E=
B=
C=
Q5
E=
B=
C=
Q6
E=
B=
C=
Q7
E=
B=
C=
Q8
E=
B=
C=
Q9
E=
B=
C=
Q10
E=
B=
C=
Q11
E=
B=
C=
Q12
E=
B=
C=
Q13
E=
B=
C=
Q14
E=
B=
C=
Q15
E=
B=
C=
Q16
E=
B=
C=
If I did it right...
I set the oscilloscope to CH1/0V and I connect the output. It doesn't move away from the 0V line. I'm coupling with AC, if I couple with DC it does move a bit. 20mV/Div it goes 0.8/1Div so it's 16mV?
Voltage at resistors is 0 and changing bias doesn't affect anything.
I guess I have to make a table of measurements...
Sorry English ain't my 1st language and I try understand all the steps correctly.
I set the oscilloscope to CH1/0V and I connect the output. It doesn't move away from the 0V line. I'm coupling with AC, if I couple with DC it does move a bit. 20mV/Div it goes 0.8/1Div so it's 16mV?
Voltage at resistors is 0 and changing bias doesn't affect anything.
I guess I have to make a table of measurements...
Sorry English ain't my 1st language and I try understand all the steps correctly.
Use your DMM set to voltage to measure voltages.
Start with a high voltage setting and when it confirms a very low reading switch down to a the next more sensitive setting.
When you get to 199.9mV ac or dc, you can read to a resolution of 0.1mV ac or dc.
Don't assume a nearly zero reading on an AC scale is automatically safe to switch over to DC. Do each (ac or dc) at the highest and check both as each intermediate setting.
Start with a high voltage setting and when it confirms a very low reading switch down to a the next more sensitive setting.
When you get to 199.9mV ac or dc, you can read to a resolution of 0.1mV ac or dc.
Don't assume a nearly zero reading on an AC scale is automatically safe to switch over to DC. Do each (ac or dc) at the highest and check both as each intermediate setting.
Well now I have all connections made and working but still no avail.
Next step is the table of measurements.
Next step is the table of measurements.
IN = 1Vpp f=1kHz
AC-RMS
Q1
E= 320mV
B= 460mV
C= 345mV
Q2
E= 320mV
B= -
C= 345mV
Q3
E= 20mV
B= -
C= 317mV
Q4
E= 344mV
B= 344mV
C= -
Q5
E= -
B= -
C= 156mV
Q6
E= 20mV
B= -
C= 20mV
Q7
E= 6mV
B= -
C= 125mV
Q8
E= 50mV
B= 600nV
C= 200nV
Q9
E= -
B= 6mV
C= 170mV
Q10
E= -
B= -
C= 170mV
Q11
E= -
B= -
C= 170mV
Q12
E= -
B= -
C= 170mV
Q13
E= 700nV
B= 30mV
C= -
Q14
E= 800nV
B= 700nV
C= -
Q15
E= 800nV
B= 700nV
C= -
Q16
E= 800nV
B= 700nV
C= -
AC-RMS
Q1
E= 320mV
B= 460mV
C= 345mV
Q2
E= 320mV
B= -
C= 345mV
Q3
E= 20mV
B= -
C= 317mV
Q4
E= 344mV
B= 344mV
C= -
Q5
E= -
B= -
C= 156mV
Q6
E= 20mV
B= -
C= 20mV
Q7
E= 6mV
B= -
C= 125mV
Q8
E= 50mV
B= 600nV
C= 200nV
Q9
E= -
B= 6mV
C= 170mV
Q10
E= -
B= -
C= 170mV
Q11
E= -
B= -
C= 170mV
Q12
E= -
B= -
C= 170mV
Q13
E= 700nV
B= 30mV
C= -
Q14
E= 800nV
B= 700nV
C= -
Q15
E= 800nV
B= 700nV
C= -
Q16
E= 800nV
B= 700nV
C= -
Sorry I half assed that, wasn't sure when I started and clock was kicki' my back there.
I'll let you know tomorrow for the values.
Thank you. You are really helpful.
I'll let you know tomorrow for the values.
Thank you. You are really helpful.
Hey! It turned out to be another bad nreadboard. Now it's working almost as it should, but there is still something that needs to be handled.
If I ran it 20V supply can't give enough current, now it's running at 14 volts.
The negative half clips just a little and bias doesn't seem to affect still yet to anything.
If I ran it 20V supply can't give enough current, now it's running at 14 volts.
The negative half clips just a little and bias doesn't seem to affect still yet to anything.
First thing is to check that there is no DC offset.
If that is OK then what is the voltage across R22, the resistor used for sensing the output stage current.
Does that voltage vary as you alter the bias preset ?
If that is OK then what is the voltage across R22, the resistor used for sensing the output stage current.
Does that voltage vary as you alter the bias preset ?
No noticeable DC-offset.
IN 200mVpp R22 is for 8-Ohms 180mV. It does not vary.
IN 1,4Vpp R22 is for 8-Ohms 125mV. It does not vary. Negative clipping becomes obvious
IN 200mVpp R22 is for 8-Ohms 180mV. It does not vary.
IN 1,4Vpp R22 is for 8-Ohms 125mV. It does not vary. Negative clipping becomes obvious
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I'm pretty sure it's not breadboard anymore. I measured all the BCE's earlier and all of them seem to be fine and I can give you the measurements by monday. I forgot them to the lab...
Then again. If I didn't fail my measurement when determining the dc offset. But there was a small thing I noticed, I measured it twice and it had changed, so maybe there could be that I've missed something that isn't right.
I got a dc meter and put it at the output when no signal was applied.
How to Measure DC Offset: 5 Steps (with Pictures) - wikiHow - Like this.
Then again. If I didn't fail my measurement when determining the dc offset. But there was a small thing I noticed, I measured it twice and it had changed, so maybe there could be that I've missed something that isn't right.
I got a dc meter and put it at the output when no signal was applied.
How to Measure DC Offset: 5 Steps (with Pictures) - wikiHow - Like this.
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Yes, it is just the steady state DC voltage present at the output.
It is unusual for a DC offset to be a lowish value, usually it is a hard swing to one or other of the rails as the feedback loop is broken. Indeterminate values can sometimes indicate oscillation.
It is unusual for a DC offset to be a lowish value, usually it is a hard swing to one or other of the rails as the feedback loop is broken. Indeterminate values can sometimes indicate oscillation.
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