What is bias current? Thank you

The bias current is the base DC current of the input transistor of the first stage amplifier.

This current ensures the amplifier's operating range and provides a DC operating point for the amplifier. Because op amps require the widest possible range of common-mode input voltages and are directly coupled, it is not possible to integrate a current source that provides bias current on the chip. Therefore, they are all designed to be open-base, and the current is provided by the external circuit.

Because the value of the bias current of the first stage is very small, UA to NA order of magnitude, the input resistance and feedback resistance of the general arithmetic circuit can provide this current. The bias current value of the op amp also restricts the input resistance and feedback resistance values from being too large, so that the voltage drop on the resistor is comparable to the operating voltage and affects the calculation accuracy.

It is the base average current when there is no input signal.

It is generally provided by a resistor.

In this way, when the signal is zero, the output is not zero, but a positive value; When the signal current is negative, the output current is not zero but becomes smaller, the more negative the signal, the smaller the output, so that you can know how negative the signal is.

If there is no bias current, then when the signal is negative, the output is zero regardless of how negative it is, and there is no difference.

If you don't need to know how negative the signal is, you can skip the bias current and save the resistor that provides the bias current (commonly known as the bias resistor).

The basic current to ensure the normal operation of the circuit is generally the most common in the amplification circuit.

Analog electronics are talked about in it.

It seems to be the base current when the transistor is quiescent.

Bias voltageMeaning: It refers to the transistor amplification circuit when the transistor is in the amplified stateBase– The voltage that should be set between the emitters and between the collector and the base.

Because to amplify the transistor, the pn junction between its base and emitter.

It should be positively biased, and the PN junction between collector and base should be reversed.

What is a Bias Circuit:In order to amplify the signal voltage without distortion, the amplifier composed of transistors must ensure that the transmit junction of the transistor is positively biased and the collector junction is reversed. That is, its working point should be set.

The operating point is to set the base, emitter, and collector of the transistor at the required potential (which can be calculated according to the calculation) by setting the external circuit. These external circuits are called bias circuits (which can be understood as circuits with positive and negative biases of PN junctions), and the current supplied by the bias circuits to the transistor is called the bias current.

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Problem description: There is also p=ui=cu(du dt), i=(dq dt)=c*(du dt), why is there a d in front of it, what does it mean, i=(dq dt)=c*(du dt).

Analysis: DC bias voltage refers to the voltage that should be set between the base and emitter and between the collector and the base when the transistor is amplified in the transistor amplification circuit.

This is because in order for a transistor to be amplified, the PN junction between the base and emitter should be positively biased, and the PN junction between the collector and base should be reversed. Therefore, the circuit that sets the forward bias of the transistor-based shot junction and the reverse bias of the set base junction to make the transistor work in the amplified state is referred to as the bias circuit (which can be understood as the circuit that sets the positive and negative bias). The key to making a transistor operate in the amplified state is its base voltage, so the base voltage is also called the bias voltage.

In addition, the voltage setting that enables the transistor to operate in the amplified state is provided by the DC power supply when there is no signal.

Therefore, the DC bias voltage of a transistor can be defined as follows: when the transistor has no signal, the DC voltage applied between its base and emitter is called the DC bias voltage of the transistor.

The d in p=ui=cu(du dt),i=(dq dt)=c*(du dt) is the differentiation, and du dt is the differential of the voltage u versus t, which can be understood as the "small" change of voltage when the time is "small". Since the current flowing through a capacitor is related to the voltage at its ends. And when the capacitor is charged and discharged, the voltage at both ends of the capacitor is constantly changing.

Therefore, the current flowing through the capacitor is equal to the change in charge q accumulated across the capacitor per unit time (tiny), which is expressed as i=(dq dt). Moreover, the change in charge q accumulated at both ends of the capacitor reflects the change in voltage at both ends: q = cdu.

So there is: i=(dq dt)=c*(du dt).

The d used here is the micro-slag fraction operator, which is introduced in advanced mathematics. If you don't study advanced mathematics, you can ignore it and understand it as "small changes".

They speak very professionally. I'll give you a layman's point. First of all, take it literally.

The meaning of bias is not right, that is, next to it. The meaning of setting can be understood as setting. When they are put together, they are set next to each other, and when the voltage and current are added at the back, together they are set by the voltage next to the side and the current set next to them.

Then why set it next to it, this is because in the circuit, in order for the tube to work, you must first meet the needs of the tube, you meet it, it can work for you, the circuit itself has limited conditions, so we artificially set it in the circuit to set a required voltage or current. This is biased in the circuit, and you can remember the setting next to that sentence anyway.

This thing, self-defined, in order to make your tube work in the state you need and input it to achieve the voltage or current that can reach this state, has reached the working state we want, then the value of voltage and current is its bias voltage and current in this working state, the tube has a lot of working states, there is no need to stick to what area and what area of working voltage and current. The amplification area, the other area, we can also give him the appropriate value when we need it, and this is the bias parameter we want.

It is the voltage and current that allows the transistor to enter the amplification area.

The components in the circuit require the right voltage and current, and the task of the bias circuit is to configure the necessary electrical parameters for them.

The bias current is one of the parameters to be configured for the bias circuit.

The most common bias circuits are transistor circuits. Examples:

Because a triode has three working states, namely amplification, cut-off, and saturation. Through different paranoid circuits, the transistor can be made to work in different states. Below is a typical common emitter bias circuit.

The bias current is the base current of the triode, and in order to make the triode on, a certain voltage and current must be added to the base, so that the triode can work normally. The bias circuit is the signal circuit connected to the base of the triode, and the circuit that provides the bias signal for the operation of the triode.

A circuit that provides a quiescent (when there is no signal input) operating current to an amplification circuit (or other circuit) is called a bias circuit, and the resulting current is called a bias current.