The OADB is a prototyping board dedicated to operational amplifier circuits. The board is based on a generic structure so that almost all OA topologies can be realized, with several features regarding power supply, reference voltage and measurement.
Below is the functional block diagram of the board.
Each OA input has a dedicated optional input stage, also based on a selectable dual operational amplifier. The following functions can be performed:
- Buffer or amplifier: when using RF generator, the input can be matched to 50R impedance and amplified to the desired level.
- Summing amplifier: especially useful when designing filters, to deliberately add some noise to the data signal.
Generic operational amplifier circuit
The operational amplifier to check is a dual OA using the standard pinout in SOIC-8 package. This way, the same board can be used to compare two circuits.
Input stages connection
All OA inputs can be connected together, so that both operational amplifier of the dual IC can share the same input stage. This feature is useful for comparing two circuits with a common input signal (no need to move the input connection).
Reference voltage (VREF)
Some circuits requires a reference voltage (VREF) for biasing purpose:
- Each VREF can be either adjusted internally with a resistor divider, or set by an external voltage through a dedicated connector.
- All VREF can be connected together, so that both operational amplifier of the dual IC can share the same reference.
Each OA output has a dedicated optional output stage, also based on a selectable dual operational amplifier. The following functions can be performed:
- Buffer or amplifier: when using RF equipment, the output can be buffered to enable 50R load.
The board has 3 main power supplies:
- VCC-IN which powers all input stages with an optional regulator.
- VCC-OA which powers the generic operational amplifier circuit with an optional regulator. A jumper is available for current measurement.
- VCC-OUT which powers all output stages with an optional regulator.
The regulators use a generic SOT23-5 package, compatible with adjutable and fixed pinouts, with bypass capacitor or not.
All inputs or regulators outputs can be connected together, so that all configurations are possible (single power for all the board, dedicated regulators, etc...).