The emitter can drive a motor or loudspeaker in circumstances where the signal to the base might not be even powerful enough to turn a led on. Unity voltage gain capability of voltage follower circuit makes it eligible for obtaining desired output voltage that is analog as well as as digital.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. What are the practical reasons to use a voltage-follower? Ask Question. Asked 7 years, 11 months ago. Active 4 years, 3 months ago.
Viewed 41k times. Add a comment. Active Oldest Votes. However, by inserting an ideal voltage follower between the amplifier and the load: simulate this circuit The overall loaded voltage gain is now , the unloaded voltage gain.
A voltage divider is not a regulator and you could end up smoking a resistor if a voltage divider is used to step-down a power source. With or without a voltage divider circuit, the voltage follower, or voltage buffer, offers a means to transfer a voltage source signal from one impedance level to another without affecting current. Voltage followers are used to match impedance in other circuits, too. Note that there is also a current buffer, which preserves the current signal source, rather than voltage signal source.
In this way, the magnification or other performance of the previous stage can be kept unchanged. Otherwise, if the previous-stage input impedance is large, and the latter stage is small, the signal will definitely be distorted. For example, if a sinusoidal voltage waveform with a peak value of 10V, the sinusoidal peak value loaded to the latter stage may only be 8V.
After adding a voltage follower, the waveform loaded on the input of the voltage follower will basically not change, and the input-output stage voltage ratio is very close to unity. So there will be no distortion. Since the output impedance of the voltage amplifier is generally relatively high, usually in the range of several kiloohms to tens of kiloohms. If the input impedance of the subsequent stage is relatively small, part of the signal will be lost in the output resistance of the previous stage.
At this time, a voltage follower is needed to buffer from it. Another advantage of applying a voltage follower is that the op amp input impedance is increased, so that the capacity of the input capacitance can be greatly reduced, which provides a prerequisite guarantee for the application of high-quality capacitors. Another question, what about isolation? Because the op amp input impedance of the voltage follower is very large, it can be approximated as an open circuit.
Of course, this open circuit is for the previous circuit. In this case, the previous circuit will not affect the subsequent circuit. However, "open circuit" means what, is it really open? No, the previous voltage is transmitted, but the corresponding current is not transmitted. This is the isolation effect. More than one doesn't work. In this case, you can add a voltage follower, so that the voltage is still the original voltage, but the driving ability has improved. Of course, the output capacity is not increased out of thin air, but comes from the input power of the op amp.
In electronics, the diode has current amplification capability, and its source of amplification capability also comes from the power supply. In Hi-Fi circuits, the controversy about negative feedback has been around for a long time.
In fact, if there is no negative feedback, most amplifying circuits will not work well. However, due to the introduction of a large loop negative feedback circuit, the back EMF of the speaker will pass through the feedback circuit and be superimposed with the input signal.
The sound quality is blurred and the clarity is reduced. Therefore, some of the final stages of the power amplifier adopt a circuit without large loop negative feedback, trying to eliminate the disadvantages by disconnecting the negative feedback loop. However, since the operating current of the final stage of the amplifier varies greatly, its distortion is difficult to control.
Here, the function of the voltage follower is just for the application. Putting the circuit between the front stage and the power amplifier can cut off the interference effect of the back electromotive force of the speaker on the front stage, so that the clarity of the sound quality is greatly improved.
Figure 1. Op Amp Voltage Follower Schematic. The output and the inverting input terminal are connected in series with a 10k resistor to ensure excellent characteristics. An ac signal is input at the non-inverting input terminal. Of course, dc and ac are all okay, so you will get a very high voltage at the output terminal.
AC voltage that is similar and has excellent load capacity, with buffering and isolation effects. The problem of using a voltage follower to keep the operational amplifier stable , that is, how to reduce the oscillation in the amplifier circuit using negative feedback to maintain stability, there is still no final conclusion. The ideal operating state of the op amp is that the output voltage and the input voltage are in phase, that is, when the applied voltage at the negative input causes the output to increase, the op amp can reduce the increased voltage accordingly.
However, there is always a difference in phase between the input and output in reality. It becomes a state of positive and negative collapse. If it falls into this state in a specific frequency band and still maintains the original amplitude, then the output frequency and oscillation state will continue. The below graph depicts the setting behavior of the circuit. Setting Behaviour. With this one might be in the thought that does this kind of circuit is useful in any application.
Let us now know the detailed scenario behind the purpose of voltage follower and how it is arranged to suit various applications. When there is the transmission of the voltage signal from one sub-circuit to another, the output impedance of the source and the input impedance of the load sub-circuits have to be considered.
This forms a voltage divider and correspondingly the voltage transfer level is based on the proportion of input and output impedance values. For effective voltage transfer, there is a need for a source circuit having minimal output impedance and a load circuit having high input impedance values.
This kind of arrangement is simple and suitable to solve complicated impedance relationships. When there happens signal transfer from high-output impedance sub-circuit to low-input impedance sub-circuit, then the voltage follower that is in between these sub-circuits makes sure that there is the complete transfer of voltage to the load section.
Here, a resistive voltage divider delivers reference voltage V REF , however, the output impedance is not minimal mainly when the high-value resistors are employed in the approach of decreasing current utilization. It is known that everyone uses a voltage follower circuit to generate an output signal following the input signal.
Because the device is easily vulnerable to oscillations and this shows an impact on the voltage follower stability.
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