The first part of this circuit from the capacitor and the resistor that it sees down to ground forms a high-pass filter, an RC high-pass filter. Shouldn’t something be said about switching times? Therefore, the voltage at the output is the same as the voltage at the input. I suspect the transistors aren’t designed to carry that much current so I need a higher rating transistors Correct me if I’m wrong. So in order to get this voltage, we have to choose our resistors that allows for this voltage to appear at the base.

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We want the second capacitor to react similarly to the first, in regard to the frequency that we’re dealing with. After putting a CRO on the circuit and looking at the waveforms and DC operating points I made a number of modifications and increased the power supply to 14V which resulted in a power output of around bbuffer.

An emitter follower is circuit is a transistor circuit in which the voltage at the emitter follows the input voltage. So you can see it’s not completely a voltage follower.

Simulation Models

Now we move onto the second capacitor. Refer to the above mentioned app note for more on this circuit However, for all basic purposes, it 2n2222s very well as a low precision buffer.

The reason the transistor cannot swing 2n2222w to ground is because the transistor will not on unless the diode is switched on and that happens at about 0. This means that any frequency at that range or lower will be filtered out to ground.


Single transistor level up shifter Ask Question. It looked a little suspect 2nn2222a me This is when one needs an alternative, such as a two-transistor set-up mentioned in the question, to drive the output rail harder. We will now get into the details of why the various components are needed for the circuit and how to choose the values for them.

So this is the first consideration. If you choose a DC operating voltage too high, you will cause the singal to clip at the top of the waveform.

2n2222a, the emitter voltage is equal to the base voltage minus the voltage drop across the diode. For a lot of the values of the components we actually compute, you won’t be able to find those precise values.

The circuit configuration you have is called an emitter-follower, and it not used for switching, its used for buffering analog signals typically. By biasing the base voltage right in the middle of the ceiling and floor, it allows for maximum swing of the AC signal, called maximum peak-to-peak excursion. Therefore, we want to bias the base voltage that it falls in between these values.

Next, we have to decide the value of the R E resistor. So we’ll talk about this now. Therefore, if a voltage line needs to be buffer it can be connected to the input of this circuit and the load that needs to be 2n2222a connects to the output of this circuit.

Resistors R 1 and R 2 are in parallel. What is R EQ in this case?

Single transistor level up shifter – Electrical Engineering Stack Exchange

This transistor is just a switch, right? A reverse wired diode across the motor terminals is a good idea also. With a proper layout that would have been immediately obvious, and might help you see what is really going on in the circuit too.


In order to correctly design an emitter follower circuit, several factors must be taken into account, including how much DC voltage is supplied to the collector of the transistor, how much current is desired to be passed through the transistor, and the frequency cutoff of the AC signals entering the input.

Post as a guest Name. EVen though current can take those paths, it’s ultimately what a capacitor sees that determines the real resistance that it encounters. Any lower, and the level becomes problematic. On the figure, C represents the collector side of the transistor and E represents the emitter side, R represents the 12 volt relay and M represents the Multi-meter.

Simulation Models: 2NA

If you’re dealing with sound signals, the frequency range that is audible to humans buffe 20Hz to 20,Hz. Positioning the transistor at the midpoint of those voltages allows for the maximum swing of the AC signal from the ceiling to the floor.

Therefore, the voltage at the output is the same as the voltage at the input. One, we have to decide the cutoff frequency of the circuit.

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