Abstract: A high precision current control circuit (current mirror) is disclosed. As in prior current mirrors, a reference voltage is generated from the input reference current. An operational amplifier is placed between the reference diode and the bases of the controlled transistors to provide precise reproduction of the reference voltage with ample current to drive many controlled current sources or current sources with high multiplication ratios from the reference current. As compared to prior emitter follower drivers, a lower voltage threshold of operation from an external proportional control results. Lower power supply voltage is supported, since one diode drop is removed from the reference current path.

Abstract: A frequency synthesizer apparatus is disclosed which combines a digital multiplier in the count down and phase comparison section with an oscillator entirely contained on an integrated circuit. Inclusion of the digital multiplier allows simultaneous realization of high loop bandwidth and fast tuning speed. The large loop bandwidth facilitates use of a totally integrated oscillator, which was heretofore not useable because of inferior phase noise characteristics. An integrated filter further enhances loop bandwidth while maintaining stability. Synchronizing the modulus switching of a multi-modulus prescaler with the multiplier coefficient minimizes spurious responses in the synthesized output.