| 摘要 |
PURPOSE:To improve the picture quality by connecting an auxiliary current source to an emitter of the 5th transistor (TR) so as to allow a current of the current source to be made dependent on a control current source inserted to an emitter of the 1st and 2nd TRs thereby making the amplitude of an output signal constant independently of the current change of an input signal to be modulated. CONSTITUTION:The circuitry is constituted that the emitter of the TR5 is grounded via the auxiliary current source 18 and also the emitter of the TRs 1, 2 is grounded respectively via current sources 10, 11. Then a compensation current Icomp is selected as expressed in Equation (where; Ig is a current flowing to a resistor 9 and Is4, Is5 are saturated currents of TRs 4, 5), allowing an output amplitude Vpp' of a current control oscillator to be made equal to a voltage Vo between an output terminal 16 and a power supply voltage Vcc, thereby making the amplitude of an output signal constant at all times independently of the current change in an input control current Iin. Thus, the current control oscillator is used as an FM modulator for a luminance signal of a VTR, allowing to improve the picture quality. |
