Hi all,
I am designing a simple common emitter amplifier for an audio application. The circuit consists of a PN2222a transistor, base resistor, and collector resistor. The first attachment shows my calculations for the component values, along with voltages and currents measured using both a SPICE simulation and circuit build. The build is shown in the second attachment. Vin should be 68.3mVrms, 20Hz. It got cut off in the picture.
The measurements from the circuit do not match up with the simulation. For example, collector voltage is 8.56 V, where it is 6.23 V simulated. There is only a .14 V drop across the collector resistor. It should be much higher than that, and I cannot figure out why it is so low. Also, DC collector current is only marginally larger than base current. Output voltage is 0 Vrms. I measured the DC voltages without any AC going into the circuit, which I believe is the correct way to do it.
I understand that Vc should be about half of Vcc to allow for voltage swing, and also that Ic = Ib x Hfe. For a NPN to be in forward active mode, Ve < Vb < Vc. I do not think the circuit I built is indeed in forward active mode, because it does not seem like any significant amount of current it being passed through to the collector.
Can anyone find a mistake in my calculations or circuit build?
I am designing a simple common emitter amplifier for an audio application. The circuit consists of a PN2222a transistor, base resistor, and collector resistor. The first attachment shows my calculations for the component values, along with voltages and currents measured using both a SPICE simulation and circuit build. The build is shown in the second attachment. Vin should be 68.3mVrms, 20Hz. It got cut off in the picture.
The measurements from the circuit do not match up with the simulation. For example, collector voltage is 8.56 V, where it is 6.23 V simulated. There is only a .14 V drop across the collector resistor. It should be much higher than that, and I cannot figure out why it is so low. Also, DC collector current is only marginally larger than base current. Output voltage is 0 Vrms. I measured the DC voltages without any AC going into the circuit, which I believe is the correct way to do it.
I understand that Vc should be about half of Vcc to allow for voltage swing, and also that Ic = Ib x Hfe. For a NPN to be in forward active mode, Ve < Vb < Vc. I do not think the circuit I built is indeed in forward active mode, because it does not seem like any significant amount of current it being passed through to the collector.
Can anyone find a mistake in my calculations or circuit build?
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