Less than that over a range of temperatures and taking tolerances of resistors into account. Worst case (at 25☌) the DC collector voltage would be between 6.15V and 3.37V, so it could work with output amplitudes up to around 6Vp-p before clipping. If you use the latter, with a 10V supply, R2 = open and RL = 2.5K then R1 would be around 1.1M. BCX70H is even tighter specified (180-310 25☌). So if you have a transistor like the common 2SC2712Y you know the hFE is between 120 and 240 so you can calculate the required resistor for a given load resistance. R2 doesn't really do much of value in this circuit.įor it to act as an amplifier, the base is biased with a current from the supply to result in the transistor being in the active mode. It also makes the input less prone to 'blocking' caused by the Base rectifying large AC signals and building up a negative bias on the coupling capacitor. in a switching circuit, or for peak detection of an AC waveform. However it is useful in situations where a well defined bias voltage is required, eg. This is not a good biasing scheme for a linear amplifier because it lowers the source impedance which makes the relationship between Base current and source voltage more logarithmic than linear, and it makes the bias point more temperature sensitive. If current going through the divider is much larger than the Base current it will set the bias voltage fairly accurately. It won't get much above 0.7V, but as bias voltage is reduced the Base current decreases so it has less effect. VB voltage always be around 0.7V no matter the voltage divider output? When emitter branch is connected straight to the ground, wouldn't the
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