 # Quick Answer: How Much Voltage Does A Transistor Need?

## How much voltage is needed to turn on a transistor?

In reality, we need a non-zero forward voltage drop (abbreviated either Vth, Vγ, or Vd) from base to emitter (VBE) to “turn on” the transistor.

Usually this voltage is usually around 0.6V..

## Can a transistor amplify DC?

Yes,by using direct coupling(transistors) amplifier we will amplify low frequency (DC) signals. … A transistor is certainly capable of taking a small-current input signal and controlling a high-current output at the same voltage, thereby amplifying the power of the input signal whether it’s AC or DC.

## Why VCE SAT is 0.2 V?

Because the charge carriers injected from the base effectively eliminate the depletion zone between the collector and emitter. The collector current doesn’t have to overcome the P-N junction potential because the base current has neutralized it.

## How do you calculate voltage across a transistor?

Use the formula Ie = (Vbb – Vbe)/[Rb/(Beta + 1) + Re] where Ie is the variable for the emitter current and Vbe is the base to emitter voltage. Set Vbe to 0.7 volts, which is the standard for most transistor circuits.

## Do transistors increase voltage?

During the negative alternation of the input signal, the transistor current increases because the input voltage aids the forward bias. … This permits the collector voltage (VC) to change with an input signal, which in turn allows the transistor to amplify voltage.

## Why is VBE 0.7 V?

For an unbiased transistor, considering only the BE junction which is a pn junction diode, 0.7V is the potential barrier. In an npn transistor base is positive(p) and emitter is negative(n). … But in a pnp transistor the base is negative(n) and emitter is positive(p) so the vbe=-0.7V.

## What is the minimum voltage?

Minimum voltage is the voltage which has to be applied to the device, to gain the desired operation/output. The device may not operate, if a voltage, below the minimum rated voltage, is applied.

## How do you calculate the resistance of a transistor?

To calculate the base resistor, subtract the B-E 0.7V from the driver voltage and divide by the base current: 4.5-0.7 = 3.8V / 400uA = ~9.5K ohms max. The difference in CE drop between a factor of ten and using the beta is neglible for relatively slow on/off circuits, and it lowers the driver current requirement.

## How do you amplify voltage?

This circuit uses a pair of resistors as a voltage divider to control exactly how much voltage is placed across the base and emitter of the transistor. The AC signal from the input is then superimposed on this bias voltage to vary the bias current. Then, the amplified output is taken from the collector and emitter.

## How do you increase DC voltage?

To increase DC voltage in a circuit, we place the individual DC voltages in series in a circuit. Here you can see there are 3 DC voltage sources placed in series, since the negative side of each source connects to the positive side of the other source.

## Is VBE always 0.7 V?

VBE is the voltage that falls between the base and emitter of a bipolar junction transistor. VBE is approximately 0.7V for a silicon transistor. For a germanium transistor (which is more rare), VBE is approximately 0.3V. Again, this formula, can be used for either silicon or germanium transistors.

## Is there a voltage drop across a transistor?

Note: The transistor isn’t a perfect switch. When off there is a small current that flows (~50nA for the 2N3904) and when on it has a small voltage drop (~0.2V depending on the collector & base currents). … Note: When the transistor is turned on there will be about a 0.7V drop across the base emitter junction.

## Why is voltage divider bias more stable?

The voltage divider is very stable in that it is a RATIO. So, the output does tend to be a very precise PERCENTAGE of the power supply. … If this is biasing a CE amplifier, the Vbe is exponentially, so this is a huge variation and the BJT Vbe varies as well so the target bias voltage also varies.

## How transistor is used as a switch?

One of the most common uses for transistors in an electronic circuit is as simple switches. In short, a transistor conducts current across the collector-emitter path only when a voltage is applied to the base. When no base voltage is present, the switch is off.

## Can you bypass a transistor?

If you add base resistors to both transistors, there is no risk in bypassing the transistors in your diagram. You basically turn the transistor in a diode and you have to limit the base current / GPIO-pin current from your microcontroller as the base-emitter voltage will be about 0.7V.