Hi guys.
I'm trying to build a gain stage for a small pre-amplifier that has a gain of 5. I am using a common emitter configuration with an NPN transistor.
The input source is a 10mV peak to peak signal from say a microphone, for examples sake feeding in a 1kHz signal.
It is running of a 12v supply and i want to bias the transistor to run at its Quiescent point of 6v.
I've used the following guidlines to come up with this resistor values as follows:
(http://www.rason.org/Projects/bipolamp/bipolamp.htm)
Vcc = 12v
Ic = 2 mA
hFE = 5
Ib = Ic/Hfe = 0.002/5 = 0.0004 (.4 mA)
R1 = half Vcc / IC = 6/.002 = 3000
R2 = 1 (chosen voltage over emitter) / (Ib + Ic) = 1 / (.002 + .0004) = 416.7
R4 = 1.7 (base voltage due to volt drop Vbe) / 10 x Ib = 1.7 / .004 = 425
R3 = needed R3 Voltage drop / R4 current + Ib = 10.3 / 0.0044 = 2340
summarised: R1 = 3K, R2 = 416, R3 = 2340, R4 = 425.
The problem:
When i simulate this using Multisim i experience absolutely no gain. I've attached a picture to show the circuit and how i have hooked up the oscilliscope.
Can someone please help me with this? I am a beginner to electronics. In case i've confused you my goal is to achieve a gain of 5 while also biasing the transistor at 6v.
Thank you.
I'm trying to build a gain stage for a small pre-amplifier that has a gain of 5. I am using a common emitter configuration with an NPN transistor.
The input source is a 10mV peak to peak signal from say a microphone, for examples sake feeding in a 1kHz signal.
It is running of a 12v supply and i want to bias the transistor to run at its Quiescent point of 6v.
I've used the following guidlines to come up with this resistor values as follows:
(http://www.rason.org/Projects/bipolamp/bipolamp.htm)
Vcc = 12v
Ic = 2 mA
hFE = 5
Ib = Ic/Hfe = 0.002/5 = 0.0004 (.4 mA)
R1 = half Vcc / IC = 6/.002 = 3000
R2 = 1 (chosen voltage over emitter) / (Ib + Ic) = 1 / (.002 + .0004) = 416.7
R4 = 1.7 (base voltage due to volt drop Vbe) / 10 x Ib = 1.7 / .004 = 425
R3 = needed R3 Voltage drop / R4 current + Ib = 10.3 / 0.0044 = 2340
summarised: R1 = 3K, R2 = 416, R3 = 2340, R4 = 425.
The problem:
When i simulate this using Multisim i experience absolutely no gain. I've attached a picture to show the circuit and how i have hooked up the oscilliscope.
Can someone please help me with this? I am a beginner to electronics. In case i've confused you my goal is to achieve a gain of 5 while also biasing the transistor at 6v.
Thank you.
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