Limiting circuits for rail-to-rail output stages of low-voltage bipolar operational amplifiers

This paper describes a family of limiting circuits for protecting rail-to-rail output stages of low-voltage bipolar operational amplifiers. The circuits limit the output voltage and output current. The output voltage is limited to avoid delay caused by saturation of the output transistor. The output current is limited to avoid destruction of the output transistor. Measuring of the output current is done without reducing the output voltage range. The limiting level of the limiters can easily be programmed. All circuits have a very short control loop ensuring stability and the stand-by current consumption is low. The circuits have been thoroughly simulated and are currently being integrated in a 2 μm bipolar process