Make Lm324 Op Amp Swing Rail-To-Rail

  
By using two CMOS inverters, the output for an LM324 op amp can be increased from 3.5 Vpp to 4.9 Vpp.
Make Lm324 Op Amp Swing Rail-To-Rail - schematic

This circuit is only recommended for light loads (<30 mA) and for relatively slow op amps. Any CMOS inverter (74COO, 74C02, 74C14, CD4001, CD4011, etc.) can be used.