![]() For an NPN transistor, terminals of all batteries, milliammeters, and voltmeters have to be reversed. When plotted equation (13) gives the static output characteristic curves while equation (14) gives the static input characteristic curves.Ĭircuit Setup of Common Emitter Configuration of PNP Transistorįigure 4 shows the basic circuit arrangement for obtaining the static characteristics of a PNP transistor in CE configuration. Then I C and V BE be expressed in terms of V CE and I B as per the following equations. Out of these totals of four variables, the input current I B and the output voltage V CE are taken as the independent variables whereas the input voltage V BE and the output current I C form the dependent variables. Thus, we are left with two current variables namely I B and I C. Further, the current I E is ignoring, being equal to –(I C + I B). Thus, we are left with two voltage variables namely V BE and V CE. Here, the emitter is the terminal common to the input side and the output side, and this terminal have been grounded. Figure 3 shows a PNP transistor connected in a common emitter (CE) configuration. The CE configuration is the one most widely used in transistor circuits. (12) Static Characteristic Curves of a PNP CE Transistor | Common Emitter Configuration of PNP Transistor Small Signal Current gain or h FEĪt a given operating point or h FE is defined as the ratio of small collector current increment to small base current increment, keeping V CE constant. Parameter h FE is a quantity of significance in the saturation region of the transistor and is usually provided in the manufacturer’s data, particularly for a switching transistor. It is defined as the ratio of collector current to base current. DC Current Gain of CE Transistor (or h FE) | Common Emitter Configuration of PNP Transistor Thus, truly represents the large-signal current gain of a CE transistor.Įquation (10) states that is the ratio of the change in I C from cutoff to change in I B from cutoff. Hence equation (9) states that equals the ratio of collector current increment from cutoff to the base current increment from the cutoff. On rearranging equation (7) and replacing I CO with I CBO we get,īut CE cutoff condition is defined by I E = 0, I C = I CBO, and I B = -I CBO. In Si transistors, I CEO is a few microamperes while in Ge transistors, it is a few hundred microamperes. Thus, with, so that I CEO is 100 times I CO in magnitude. This I CEO is the leakage current that flows between the collector and emitter with the base open as shown in figure (2).įrom equation (6) it is equivalent that the magnitude of I CEO is much greater than that of I CO. base is open-circuited, then I CEO equals. The following equations relate the currents:įigure (2) shows that in the CE transistor the output current I C equals input current I B multiplied by plus current I CEO. In a CB transistor, I E forms the input current while I C is the output current. The Large Signal Current Gain | Common Emitter Configuration of PNP Transistor However, current flows through what has resistance between an GND terminal and a IN terminal.Figure 1 gives the basic circuit of a CE amplifier using load resistor R C. Voltages up to 5V can be supplied to the Collector-Emitter in the reverse direction as below. (If sufficient voltage is supplied to the Collector-Emitter in reverse, deterioration such as low hFE will occur. Typically this is between 5 to 7V, making the Collector-Emitter reverse voltage less than 5V. ![]() NPN: +V to Emitter, Collector grounded) is roughly equivalent to the breakdown between the Emitter and Base. Conversely, VCEO in PNP transistors is in breakdown when positive voltage is supplied to the Emitter with Collector grounded.īreakdown in the opposite direction (e.g. Is it possible to supply voltage to the Collector-Emitter in reverse?įor NPN transistors, VCEO is in breakdown when positive voltage is supplied to the Collector pin while the Emitter is grounded.
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