The overall gain (V/A) can be adjusted over a wide range by combining the gains of individual opamps and the value of the shunt resistor.
The cascaded connection of two opamps with lower gain allows for an increased bandwidth compared to a single op-amp with high gain.
The amplifier is powered by a CR2032 battery or its rechargeable version, LIR2032. The negative rail of the symmetrical power supply is created by the LM2664 charge pump.
Diodes D1 and D2 are optional and are used to reduce the supply voltage to fit the working range of the operational amplifiers (typically 5.5V).
IC4 and LED1 provide optional indication of a depleted battery.
I have designed the PCB layout for the opamps in SOT23-5 packages with both normal and reverse pinout.
Current consumption: 2,2mA @ 3V
Bandwidth (-3dB): 55kHz (2 x MCP6V81U, first stage gain: 100, second stage gain: 10)
Nicely designed! If you want to get this manufactured inexpensively and fully automatically, I might humbly recommend that you move all the surface-mount components onto one side of the PCB.
Nicely designed! If you want to get this manufactured inexpensively and fully automatically, I might humbly recommend that you move all the surface-mount components onto one side of the PCB.