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BJT stands for Bipolar Junction Transistor. It is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications.

2 votes

How this form can be induced? (BJT accurate value of vbe)

You can derive this from the Shockley equation: *Vbe = Vt(ln(Ic/Is)) so at two different currents Ic and Ic0 we have \$V_{BE} - V_{BE0} \$ = \$V_T (\ln(I_C/I_S) - \ln(I_{C0}/I_S))\$ = \$V_T \cdot \ln …
2 votes

Gain of a BJT in reverse active mode

The hfe is the ratio of collector current to base current. Due to asymmetry in the doping of collector and (more highly doped) emitter regions, the hfe will be less in the reverse active mode compared …
0 votes

high side BJT switch analysis

When Q1 is saturated Vbq2 is 15V-Vbe of Q2. Vbe of a saturated transistor is around 0.7V for reasonable base current, so Vbq2 will be about 14.3V. Ieq2 is the emitter current of Q2 and is equal to th …
1 vote

How to solve this NPN BJT circuit for DC bias values?

Assume the BJT is in active mode- start by ignoring the base current since transistor gain is high in active mode. …
4 votes

Small Signal BJT Model

From the model viewpoint, the voltage-controlled current source is pointing in the direction that an increase in input voltage leads to a decrease in output voltage. From a practical point of view, …
1 vote

Early effect bjt

You need voltage for current to flow across the junction, but that's not the significance. The abrupt drop shown in the diagram isn't quite accurate either- there is a smooth curve downward to zero as …
1 vote

Is there a single supply voltage implementation of a differential amplifier?

The input stage of the LM324 is designed to work from a single supply- input common mode range extends to the negative rail.
0 votes

BJT configurations input

Obviously (?) not for common base. Because it's common. Input is to the emitter, which give you the potential of voltage gain, not current gain. Image from Wikipedia.
5 votes

BJT triode region

As @Brian says, in the saturation region this is true. The transistor has a dynamic resistance (for very small voltage changes) of approximately Vt/Ib. So, for example, the collector of an NPN transis …
4 votes

Switching a power BJT

To look at it another way, you are giving the base of the output BJT about 4mA so it's good for switching about 5x that or 20mA. … The BJT may be somewhat more competitive if you are switching hundreds of volts. …
5 votes

How important are BJT characteristic curves when designing amplifiers?

These transistors are 'binned' so you know the hFE over a fairly narrow range. The 'R' parts have an hFE between 180 and 390 at 10mA Vce and 6V Vce, for example. So a good starting point would be 10mA …
2 votes

How to eliminate the Miller effect on BJT BC547?

Sound like you want to drive an opto-isolator with an LM231 output. The LM231 has an open-collector output and cannot source current- so it won't work with your circuit as shown. It doesn't have a q …
5 votes

Why is a BJT considered "current-controlled"?

In general you could imagine the BJT to be a current-controlled current source when finding the bias point in a linear application (large signal). …
1 vote

Why hFE(DC gain) shown on multimeter isn't equal to the datasheed hFE?

Added to get this image in here.. the nominal resistor values vary significantly between suppliers- the below is from a Motorola model with 8K & 120 ohms. As Andy's answer suggests the problem is in …
1 vote

can SOT883B package BJT transistor switch a relay with 21.1mA coil current?

It is probably adequate to switch the 3V version with about 50% more current draw ( which I think you'll need) However, unless you're counting pennies you may wish to use something like the PBSS2515 …

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