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How to compute logarithmic amplifier output voltage in Python using UliEngineering

You can easily compute the output voltage of a logarithmic amplifier using the UliEngineering Python library:

logarithmic_amplifier_output_voltage.py
from UliEngineering.Electronics.Amplifiers import logarithmic_amplifier_output_voltage

# Compute output for 1µA input current
vout = logarithmic_amplifier_output_voltage("1uA", "10k", "0.7V")
print(f"Output (1µA, 10k, 0.7V): {vout:.3f} V")

# Compute output for 10µA input current
vout = logarithmic_amplifier_output_voltage("10uA", "10k", "0.7V")
print(f"Output (10µA, 10k, 0.7V): {vout:.3f} V")

Example output

logarithmic_amplifier_output_voltage_output.txt
Output (1µA, 10k, 0.7V): -0.161 V
Output (10µA, 10k, 0.7V): -0.230 V

The logarithmic amplifier produces an output voltage proportional to the logarithm of the input current. This is essential for compressing wide dynamic range signals, audio processing, optical sensor applications, and any application where signals span many orders of magnitude. The logarithmic response allows for better visualization and processing of signals with large variations.

The output voltage is computed using the formula: $V_{out} = -V_T \ln\left(\frac{I_{in} R}{I_s}\right)$, where $V_{out}$ is the output voltage, $V_T$ is the thermal voltage (approximately 26mV at room temperature), $I_{in}$ is the input current, $R$ is the feedback resistor, and $I_s$ is the saturation current of the diode or transistor. In practice, the implementation uses the diode equation with a reference voltage offset.

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