The SGM833B is a single-supply logarithmic current-to-voltage converter for measuring the low frequency current signals over a large range from 1nA to 10mA. With capabilities such as photodiode adaptive biasing, active-shielding (guard driving), output buffer amplifier conditioning and voltage reference on a single chip, this device is optimized for measuring the power of optical signals by using a photodiode operating in the photo current mode. The measured current is converted and compressed to a logarithmic voltage by using transistor I-V characteristics and a compensation circuit.

The SGM833B operates with a single 3V to 5.5V supply and is equipped with a disable input to shut down the device. The input current (IPD) is converted to an internal 40μA/dec logarithmic scaled current that is injected into an internal 5kΩ resistance to provide an output voltage with 10mV/dB (or 200mV/dec) logarithmic slope on the VLOG output pin. This slope can be reduced by an external shunt resistor. The intercept point (the output voltage corresponding to the selected intercept current) and the scale (to change the slope) can be adjusted by the on-chip buffer amplifier.

This device is available in a Green TQFN-3×3-16L package and is specified over a temperature range of -40℃ to +85℃.