A current amplifier buffer circuit converts the impedance of electricity before sending them to the next present circuit. This makes sure that there will not be any loading in the previous function because of the next circuit.
However, this circuit has two types. Voltage buffer and current buffer. When the current buffer has a unit gain of B=1, then the buffer converts into a current follower. This article gives a detailed insight into the current followers and current amplifiers.
What Is A Current Follower?
A current amplifier or follower refers to an opposite of a voltage amplifier or follower. It contains a traditional operational amplifier with two mirrors. The current buffer that has a unit gain of B=1 refers to a current follower, current buffer unity gain.
Simply, the value of output current tracts or follows the value of current input in such a way that input signals are not amplified. Eventually, the value of the current output also does not amplify.
These amplifiers also refer to isolation buffers as they isolate both input and output terminals during the constant maintenance of output and input current flow.
Introduction To Current Amplifier
A current follower or amplifier circuit utilizes a fixed method to increase the signals of input current before sending them to the following circuit. Generally, it refers to an amplification process of input signals of current. Both current amplifiers and voltage buffers share similar qualities, yet they differ in the aspect of current loads.
Voltage buffer during the delivery of load current keeps the values of input and out voltage the same. However, the current amplifier only amplifies the input current to a fixed amount and then sends it to the following stage. Moreover, it does not affect the components of the input supply voltage. The current amplifier also uses transistors. Furthermore, it gives input in the form of a constant signal or varying waveform.
Gain Of A Current Amplifier
In electronics, gain refers to the rate of amplifying the aptitude of an amplifier. The current amplifier uses gain to increase the rate of current signal output while keeping the input signal in check. It happens because the current amplifier only amplifies the current input signal.
Characteristics Of An Ideal Current Amplifier
An ideal or standard current amplifier contains the following features and characteristics. The input impedance of the amplifier equals zero. The impedance of out must equal infinity. At the same time, the gain must not depend on the surrounding ambient conditions such as temperature and humidity. Moreover, throughout the range of input signals, the gain must remain constant. However, getting the same values for impedance can be hard, but they can act as reference values.
Reasons For Using A Voltage Follower
Voltage follower circuits do not intentionally enhance or reduce the values of input signals, nor does it remove the high-frequency noises. However, it may have some features that make it so popular. It’s technically true that a voltage follower circuit does not amplify or alter the values of input signals or frequencies, yet it helps in improving the impedance connections. While sending voltage input signals to the following circuit, one must keep a proper check of the following circuit source output impedance and circuit load input impedance.
This input impedance of the following circuit’s load and circuit power supply output impedance creates a voltage divider. Thus, the transmission of voltage relies on the ratio of input to output value of impedance. An effective transfer of voltage needs a source that has a low value of output impedance and a high value of load input impedance.
The voltage follower contains a very high value of input impedance and a low value of output impedance. Thus making it the best and easiest solution for the impedance relationship problems. If a circuit needs to transfer signals from a high subcircuit output impedance to a subcircuit with a low value of input impedance, then place the voltage follower between both circuits. This ensures the complete delivery of the voltage to a load.
Voltage Follower Stability
As the name suggests, the voltage follower does exactly the same. It creates the signals of output which flow the signals of input. However, it may lead to serious circuit failure if not checked properly. The issue refers to stability. Like any other op-amp, voltage followers are also sensitive to oscillation.
In an amplifier with negative feedback, oscillation refers to the phase shift. It shifts that negative feedback into positive feedback. One may think that as the circuit does not amplify it whole, it may not cause any stability issues. However, voltage followers have more stability issues as it is more sensitive to oscillation as compared to any other high-gain circuit.
Therefore, an op-amp comes forward, which helps the voltage follower from oscillation and gives stable unity gain. These op-amps create a response of frequency which makes the function stable even during the configuration phase voltage follower.
A High Current Voltage Follower
The low value of voltage followers output impedance makes it an ideal circuit. It helps in driving the current even in the low load impedance. However, remember that the majority of op-amps do not deliver high current output.
Advantages Of Current Follower Circuit
The current amplifier of the follower circuit has various benefits. This includes stable circuitry, low input impedance, infinite values of output impedance, or current unity gain. Thus making it ideal for various devices and applications. However, low input impedance occurs because of the negative feedback.
How To Design A Current Follower Circuit?
The designing process of current followers requires some factors to keep in mind. Follow the following steps to create an ideal current amplifier or follower circuit. Firstly, ground the values of loads with the PNP transistor and an op-amp. The transistor acts as an active component here. It also refers to a type of resistor that senses the current. Therefore, the op-amp operates on the input of a positive value of the voltage at the rail of the power supply.
Utilize the currency converter voltage to follow the current to a convertor of voltage. This implies that each place requires a different type of converter because of some limitations. For instance, floating current, minimum current, bipolarity, unipolarity, etc.
However, in most limited situations like unipolar current, it’s better to utilize the mirror current. The current of a voltage converter connects the resistor, diode, transistor, and more transistors, which helps in producing a better value of output impedance. On the other hand, in less limited situations, use a sense resistor and differential amplifier along with the current source of Howland.
Conclusion
A voltage follower circuit refers to a non-inverting, unity-gain buffer that needs only a decoupling capacitor or an amplifier. It has a high value of input impedance with a low value of output impedance. This happens because of the buffering operation. It strengthens the signals and enables the source with high impedance to drive the load with low impedance. Whereas voltage followers also use op-amp in their setting for stable unity gain. Moreover, putting an outer transistor in the setting of voltage follower gives unity gain with a high current.
