Transistor differential circuit with exponential transfer characteristic

To provide for exactly exponential relationship between the collector current and the voltage applied between the bases of the differential circuit, two branches are provided, each containing a series connected circuit including transistors of respectively opposite conductivity type, and resistances positioned in each branch of such value that the sum of the voltage drops of connection and contact resistances arising in the respective branches are compensated. The values of the resistances are so selected that the voltage drop across the respective resistance matches the sum of the voltage drops due to the connection and contact resistances of the opposite branch.