You are probably right. So at saturation what would be the voltage between C and B? Work it out for a silicon transistor.theBEAST said:
The active mode, also known as the linear mode, is a state of operation for a bipolar junction transistor (BJT) in which the transistor amplifies a signal without significant distortion. In this mode, both the base-emitter junction and the base-collector junction are forward biased.
The largest resistor value for active mode is determined by the maximum collector current (IC) and the minimum base current (IB) required to keep the BJT in active mode. This is known as the DC current gain (hFE) of the BJT and is typically specified in the transistor's datasheet.
If the largest resistor value is exceeded, the base current (IB) may become too small to maintain the BJT in active mode. This can result in the BJT entering either the saturation region, where the collector current becomes independent of the base current, or the cutoff region, where the collector current becomes zero.
The largest resistor value for active mode is affected by the temperature due to the temperature dependence of the BJT's DC current gain (hFE). As the temperature increases, the hFE decreases, which results in a lower maximum resistor value for active mode. Therefore, it is important to consider the operating temperature when determining the largest resistor value for a BJT in active mode.
Yes, the largest resistor value for active mode can be increased by using a Darlington pair configuration, which consists of two BJTs connected in a common-emitter configuration. This configuration has a higher DC current gain (hFE) compared to a single BJT, allowing for a larger maximum resistor value for active mode. However, this also introduces a higher input capacitance and a longer turn-off time for the BJT pair.