I just made this preamp circuit, its performance is very good. But its gain is 37db and this is very high. What do I need to do to change gain? Or can I make variabke gain? I put a potentiometer on the output. This reduces the gain, but the his noise does not decrease.
No emitter degeneration will lead to high gain and high distortion too... Add an emitter resistor, maybe start with 100R?
I'd recommend actually do proper biasing of the base voltage with a divider, not just R2, then the transistor's current will be well defined and stable as the voltage across the emitter resistor is defined.
Changing to a BC549C might reduce the hiss somewhat, its the lowest noise of that family (its the TO92 version of the BC107/8/9 I believe, the BC109C was the low noise device in that family)
I'd recommend actually do proper biasing of the base voltage with a divider, not just R2, then the transistor's current will be well defined and stable as the voltage across the emitter resistor is defined.
Changing to a BC549C might reduce the hiss somewhat, its the lowest noise of that family (its the TO92 version of the BC107/8/9 I believe, the BC109C was the low noise device in that family)
I'll try adding a resistor to the emitter. There is a situation. When I connect it to the phone it does not recognize the output of this preamplifier (it recognizes it for a few seconds and automatically disables it).
But when I connect the ground of the output to +v, it works without any problems. What is the reason for this?
I don't know if I have BC549 or not. Are there any other alternatives?
But when I connect the ground of the output to +v, it works without any problems. What is the reason for this?
I don't know if I have BC549 or not. Are there any other alternatives?
The gain of your circuit in simple terms is Rc/(Re+re) where re (internal resistance of emitter diode) = 25mV / Ic . However, since your Re is zero, the gain is very high, as re is a small value.
Adding an Re could reduce the gain and also improve the linearity due to negative feedback. Besides, it would also stabilise the bias point against variations in temperature etc.
Adding an Re could reduce the gain and also improve the linearity due to negative feedback. Besides, it would also stabilise the bias point against variations in temperature etc.
I have bc549c, bc239c, bc107b, Ksp2222a, 2sc1906 transistors in my stocks. Which is better? Which one should I use?
When I connect it to the phone it does not recognize the output of this preamplifier (it recognizes it for a few seconds and automatically disables it).
But when I connect the ground of the output to +v, it works without any problems. What is the reason for this?
When I connect it to the phone it does not recognize the output of this preamplifier (it recognizes it for a few seconds and automatically disables it).
But when I connect the ground of the output to +v, it works without any problems. What is the reason for this?
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The issue with the phone could be beacuse output lacks DC path to the ground. Try to add ~ 20Kohm resistor across output (after DC blocking cap).
When ground of the output is connected to
+v , then its on higher "+"potential than output, so electrolytic capacitor is reversed polarized providing a DC path.
When ground of the output is connected to
+v , then its on higher "+"potential than output, so electrolytic capacitor is reversed polarized providing a DC path.
What kind of circuit can I add to this circuit to increase 100hz by +12db? And where should I connect it? Can you help me? It may also be adjustable.
Sounds like a Baxandall bass control could do what you want - but that's taking you to opamp circuitry, in which case you might as well do everything with opamps.