clovi_kate said:
First for a good Op-Amp preamplifier
you will need a regulated +15 Volt and -15 Volt power supply.
Schematic below shows such a good supply.
Easy to build and regulated, stable 2x15 Volt output.
It uses 3 transistors.
And one 15 Volt zener diode.
D122 in diagram.
Attachments
Hi,
I don't like this circuit too much.
1. R241 and R244 are up to no good. They just rise the input voltage required and increase the source resistance of the +-Vcc sources. This is against the purpose of a regulated power supply. R241/244 return nothing for it.
2. Having a small capacitor in parallel to a Z diode does not help much. The noise source in the Z diode has a low impedance which means that the low pass filtering works only for high frequencies.
It would help to swap D122 and C162.
3. I don't think that it is a good deal to replace a Z diode by 3 resistors, a capacitor and a transistor. The circuit amplifies the noise of D122, Q118 and whatever makes it from -vcc to -15v before using it as a reference for Q116. The hi impedance divider R247, 248, 249 adds additional noise. The single pole introduced by C165 may help a little bit, on the other hand C163 may go under against the Miller-multiplied C165. Stability of the positive supply may depend on part values.
Methinks it would be better to use the negative half of the circuit for the positive side, too. Less parts, simple regulation loop, trivial to troubleshoot and not a single resistor that couldn't vary +- 50% without consequence on circuit functionality.
4. The nominal -15V output voltage will be -15.7V if D122 is a 15V type. The +15V output depends on R247 to 249 additionally.
best regards, Gerhard
d k 4 x p @ f r e e n e t . d e
I don't like this circuit too much.
1. R241 and R244 are up to no good. They just rise the input voltage required and increase the source resistance of the +-Vcc sources. This is against the purpose of a regulated power supply. R241/244 return nothing for it.
2. Having a small capacitor in parallel to a Z diode does not help much. The noise source in the Z diode has a low impedance which means that the low pass filtering works only for high frequencies.
It would help to swap D122 and C162.
3. I don't think that it is a good deal to replace a Z diode by 3 resistors, a capacitor and a transistor. The circuit amplifies the noise of D122, Q118 and whatever makes it from -vcc to -15v before using it as a reference for Q116. The hi impedance divider R247, 248, 249 adds additional noise. The single pole introduced by C165 may help a little bit, on the other hand C163 may go under against the Miller-multiplied C165. Stability of the positive supply may depend on part values.
Methinks it would be better to use the negative half of the circuit for the positive side, too. Less parts, simple regulation loop, trivial to troubleshoot and not a single resistor that couldn't vary +- 50% without consequence on circuit functionality.
4. The nominal -15V output voltage will be -15.7V if D122 is a 15V type. The +15V output depends on R247 to 249 additionally.
best regards, Gerhard
d k 4 x p @ f r e e n e t . d e
clovi_kate said:
http://www.semiconductors.philips.com/acrobat_download/datasheets/NE_SA_SE5534_A_2.pdf
How to use it:
http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN142.pdf
Dual version:
http://www.semiconductors.philips.com/acrobat_download/datasheets/NE_SE5532_A_SA5532_3.pdf
http://focus.ti.com/docs/prod/folders/print/opa2134.html
www.analog.com
You may find lots of other interesting chips on these servers.
4558, 709 and 741 are really obsolete.
Now don't let us start a new thread on OpAmp sound...
regards, Gerhard
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