A level shift circuit comprising a current drive circuit including at least one input transistor, each having an emitter connected to a first reference potential, having a collector and having a base receiving at least one input signal, said current drive circuit includes first and second input transistors connected in parallel to differentially operate in response to first and second input signals connected to the bases of the first and second input transistors and a current source connected between the emitters of said first and second input transistors and said first reference potential;
- a load transistor circuit including at least one load transistor, each having a base connected to a reference potential, and an emitter connected to the collector of a corresponding one of said at least one input transistor, said load transistor circuit includes first and second load transistors, wherein the emitter of said first load transistor is connected to the collector of said first input transistor, the emitter of said second load transistor is connected to the collector of said second input transistor and the bases of said first and second load transistors are commonly connected and connected to a second reference potential:
- a bias current source connected between said emitter of said at least one load transistor and said first reference potential, a respective current generated by said bias current source being supplied to each of said at least one load transistor to maintain a forward base emitter voltage for each said at least one load transistor;
- a load resistor circuit including at least one load resistor connected between the collector of a respective one of said at least one load transistor and a power supply voltage;
- said bias current source further including a current mirror circuit connected to a control voltage source to shift the level of an output signal by a value defined by the control voltage source, wherein:
- said at least one load resistor includes first and second load resistors connected to the collectors of said first and second load transistors, respectively, to output first and second output signals from points at which the collectors and said first and second load resistors are commonly connected,
- said current-mirror circuit includes first, second and third current source transistors connected in parallel, wherein said first and second current source transistors have collectors which are respectively connected to the emitters of said first and second load transistors, said third current source transistor having a collector connected to the control voltage source, the collector of said third current source transistor being connected to a base thereof which is commonly connected to bases of said first and second current source transistors, and
- said current mirror circuit further includes second, third and fourth current source resistors respectively connected between emitters of said first, second and third current source transistors and ground, further comprising:
- a plurality of said current drive circuits connected in parallel, wherein each of said current drive circuits receives said input signal to be synthesized, wherein said bias current source and said emitter of said load transistor in said load transistor circuit are connected to a common connection point of said parallel current drive circuits.