Stability compensation and impedance conversion circuit for oscillator frequency adjustment loop

Abstract

The invention discloses a stability compensation and impedance conversion circuit for an oscillator frequency adjustment loop. Different from that the input control voltage in the prior art is limitedto be less than VDD and greater than GND, the input control voltage after improvement may fluctuate between VDD and GND in a large range. Since a Miller capacitor crosses the gates and drains of NM2and NM5, the input capacitances of the NM2 and NM5 become very large due to the Miller effect, resulting in that a higher-frequency oscillating signal is not input when inputting, so that the stability of the current output by a voltage-to-current module is relatively high. The circuit has the function of impedance transformation, which is capable of improving the efficiency of the oscillator.

Description

technical field [0001] The invention relates to the related field of circuits, in particular to a stability compensation and impedance conversion circuit of an oscillator frequency adjustment loop. Background technique [0002] In most cases, the commonly used oscillation circuit in the phase-locked loop is the ring oscillator in the case of low requirements. Under normal circumstances, we use the current input to the ring oscillator to control the oscillation frequency of the oscillator. Since the signal passing through the loop filter is a voltage signal, we need a voltage-to-current module to change the control voltage signal. [0003] The existing and commonly used voltage-to-current module is usually composed of a MOS tube, an operational amplifier and a resistor, wherein the gate of the MOS is controlled by the output of the operational amplifier; the resistor is connected to the source of the MOS tube, and then connected to the On the power supply or the ground; the...

AI Technical Summary

Problems solved by technology

The disadvantage of the existing circuit is that when the current demand is too large or too small, the existing circuit will cause the MOS tube to enter the linear region, resulting in low working efficiency of the MOS tube. Since the current calculation formula of the above circuit is I=Vcon / R, where I is the output current, R is the resistance value of the resistor, and Vcon is the input control voltage

Since the current is limited, the input voltage range is also limited

[0004] And when the voltage changes greatly or oscillates, this change and oscillation will be transmitted to the gate and source of the MOS tube device, resulting in an inability to maintain a constant output current

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