A logarithmic amplifier includes a logarithmic current preamplifier circuit and logarithmic amplifier circuit. The logarithmic current preamplifier circuit includes an inverting input terminal, an output terminal, and a first diode. The first diode is coupled between the inverting input terminal of the logarithmic current preamplifier circuit and the output terminal of the logarithmic current preamplifier circuit. The logarithmic amplifier circuit includes an inverting input terminal, an output terminal, and a second diode. The inverting input terminal of the logarithmic amplifier circuit is coupled to the output terminal of the logarithmic current preamplifier circuit. The second diode is coupled between the inverting input terminal of the logarithmic amplifier circuit and the output terminal of the logarithmic amplifier circuit.