Explain log and antilog amplifier circuit using Op-Amp.
Q.) Explain log and antilog amplifier circuit using Op-Amp.
Subject: electronic devices and circuitLog Amplifier Circuit using Op-Amp
A log amplifier circuit is used to compress a wide range of input signals into a narrower range of output signals. It is useful in applications where a wide range of input signals needs to be displayed or processed.
The circuit consists of an operational amplifier (op-amp), a feedback resistor (Rf), and an input resistor (Ri). The op-amp is configured as an inverting amplifier. The input signal is applied to the non-inverting input of the op-amp, and the feedback resistor is connected between the output of the op-amp and the inverting input.
The output voltage of the log amplifier is given by:
$$V_{out} = -V_{in} \cdot \log_{10} \left(1 + \frac{R_f}{R_i} \right)$$
where:
- $$V_{out}$$ is the output voltage
- $$V_{in}$$ is the input voltage
- $$R_f$$ is the feedback resistor
- $$R_i$$ is the input resistor
The logarithmic function in the output voltage equation compresses the wide range of input signals into a narrower range of output signals. This is because the logarithmic function has a smaller slope for larger input values.
Antilog Amplifier Circuit using Op-Amp
An antilog amplifier circuit is used to expand a narrow range of input signals into a wider range of output signals. It is the inverse of a log amplifier circuit.
The circuit consists of an operational amplifier (op-amp), a feedback resistor (Rf), and an input resistor (Ri). The op-amp is configured as an inverting amplifier. The input signal is applied to the inverting input of the op-amp, and the feedback resistor is connected between the output of the op-amp and the non-inverting input.
The output voltage of the antilog amplifier is given by:
$$V_{out} = -V_{in} \cdot 10^{\frac{R_f}{R_i}}$$
where:
- $$V_{out}$$ is the output voltage
- $$V_{in}$$ is the input voltage
- $$R_f$$ is the feedback resistor
- $$R_i$$ is the input resistor
The exponential function in the output voltage equation expands the narrow range of input signals into a wider range of output signals. This is because the exponential function has a larger slope for larger input values.
Applications of Log and Antilog Amplifiers
Log and antilog amplifiers are used in a variety of applications, including:
- Audio compression
- Signal conditioning
- Instrumentation
- Control systems
- Medical electronics