To provide a transmission circuit device adaptable to voltage reduction of driving voltage.

In the transmission circuit device 1, a power source voltage control circuit 10 is constituted of an analog regulator and a current voltage conversion circuit 20 is constituted only of a serial inductor 21 and a parallel capacitor 22. A multiplexer 41 upconverts a frequency of an envelope signal to an intermediate frequency (IF) generated by an oscillator 42. An operational amplifier 11 compares voltage of the upconverted envelope signal with voltage of a supply signal B output to a power amplifier 30 and outputs a control signal A for obtaining same voltage the current voltage conversion circuit 20 via a bipolar transistor 12. The current voltage conversion circuit 20 generates the supply signal B formed by multiplying voltage of the control signal A by about (a) and multiplying the current of the control signal A by about 1/a according to conversion ratio (a) determined by constants of the serial inductor 21 and the parallel capacitor 22. A power amplification part 31 amplifies a carrier signal to be output on the basis of on the supply signal B.