A differential input is applied to four bridge-connected field effect transistors. The bridge drives a differential common base transistor stage. The output can be either differential or single ended as desired taken from the transistor collectors. The circuit provides good common mode rejection and good differential response to signals over a common mode range that exceeds the voltage of the power supply.
An input stage for an operational amplifier comprises junction field-effect-transistor input devices having common sources and having their drain electrodes coupled to a PNP level shifting arrangement which in turn drives an NPN current mirror circuit. The level shifting arrangement comprises first and second PNP transistors coupled in a common base configuration with their emitters coupled to the drains of the input JFETS. The level shifting transistor are biased on so as always conduct current to the current mirror circuit.
An amplifier, preferably an integrated circuit, capable of accepting input common mode voltages below the circuit reference voltage or substrate voltage in the case of an integrated circuit. The amplifier comprises a differential voltage input having higher and lower voltage terminals, a first NMOS transistor coupled between a voltage supply and the higher voltage terminal and a second NMOS transistor coupled between the voltage supply and the lower voltage terminal. A third NMOS transistor is coupled between the voltage supply and the first transistor gate, a fourth NMOS transistor is coupled between the voltage supply and the second transistor gate and a sink resistor is coupled between the gate of the second transistor and the lower voltage terminal. A differential resistor is coupled between the gates of the first and second transistors. The first and second transistors include a source and a backgate coupled to each other and electrically isolated from the substrate with the source of each of the first and second transistors being coupled to a different one of the input terminals. The third and fourth transistors include a source and a backgate coupled to each other and electrically isolated from the substrate with the source of each of the third and fourth transistors coupled to opposite ends of the differential resistor. The circuit further includes a PMOS mirror circuit for providing an output.
A differential amplifier having input and output stages includes a linear offset operation circuit comprising sources providing a reference voltage and an offset correction voltage and a pair of transistors coupled for linear operation and responsive to the voltages for supplying differential related offset correction currents to the amplifier output stage for reducing offset characteristic of the amplifier stages and for reducing output noise and offset attributable to a noise component of the reference voltage source.
A semiconductor differential amplifier includes first and second MOS transistors of a first conductivity type acting as driver transistors, and third through sixth MOS transistors of a second conductivity type acting as load transistors. First and second input terminals are respectively connected to gate terminals of the first and fifth, and second and sixth transistors. Therefore, since input signals are applied to transistors of both the load and driver sections of the amplifier, the amplifier exhibits a higher sensitivity for detecting relatively small differences between the voltage at the first input terminal and the voltage at the second input terminal.
