This simulated circuit on the NI Multisim transmits modulated infrared signals with the audio applied to C1. Q1 can be i, BC548 and Q2 a BD136. For higher voltages, up to 12 V, Q2 must be equipped with a heat radiator. R2 and R2 adjust the modulation so that it occurs with a minimum of distortion. R1 can be changed according to the maximum current supported by the LED. This circuit can be found on the simulated website at NI Multisim (see the simulated circuits section).
