![]() Therefore, since practically no current is drawn from the power supply circuit, the power supply circuit is not loaded down.Īnd the transistor circuit are well isolated and do not interfere with each other. Practically draws no current to its input gate terminal. FETs have very large input impedances, such as on the order of 10 14 Ω, which is several teraohms (something you almost never hear about). This small amount of currentĭrawn, which then combines with the much larger current flowing from the other 2 leads can alter dynamics of the power source circuit. Second circuit, in this case the transistor circuit, which is drawing current from it. Loading is when the power source circuit is affected by a Lower resistance, it draws current from the power supply powering the base. BJTs offer much less resistance to their input terminal than FETs. For BJTs, this wouldīe the base terminal for FETs, this would be the gate terminal. Input impedance is the amount of resistance that a transistor offers on its input terminal. The second difference is the input impedance. Instead they are entirely voltage-controlled. Voltage, not current, either turns the FET on or off.įETs have such high input impedance that they practically draw no current into the gate terminal. FETs, on the other hand, are voltage-controlled. ![]() This base current then turns the BJT on, allowing for a much greater flow of current from the collector to the emitter of the This means that BJTs are switched on by a current going through theīase of the transistor. So the first thing is how both transistors operate. (BJTs) and field effect transistors (FETs).īelow we'll go over the table in more depth, so that you can get a better in-detailed explanation, if you feel the above lacked. So the above table is a good, brief explanation of some of the differences between bipolar junction transistors Important for integrated circuits that are composed up of manyĪre definitely more popular and widely used in commercial circuitsĮspecially MOSFETs, are more expensive to manufacture Gain (or transconductance) of FETs are smaller than for BJTs.Īre larger in size and therefore take up more physical space thanĬan be manufactured much smaller than BJTs. Offer greater gain at the output than FETs. Practically draw no current and therefore do not load down the power circuit ![]() Power circuit feeding it, which can cause loading of the circuit. Offer smaller input impedances, meaning they draw more current from the They only require voltage applied to the gate They require a biasing current to the baseĪre voltage-controlled. ![]()
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