用于晶体振荡器温度补偿的次方电压产生方法

为了获得更高精度的时钟源,需要对晶体振荡器进行温度补偿以便减小频率随温度的变化。对比晶体振荡器不同的温度补偿方式,模拟温度补偿具有较高的性能,而模拟温度补偿电路的主要模块就是获取与温度成次方关系的补偿电压。文中采用了一种模拟乘法器的方法来获得与温度成不同指数关系的电压,在全差分放大器的输入端接入4个MOS管,利用其工作于线性区时的电流电压关系并结合全差分放大器来实现两个模拟量之间的相乘,进而获得与温度成1次方、2次方、3次方、4次方和5次方关系的补偿电压。获得的这些电压通过加和电路叠加后即可用于晶体振荡器的高阶温度补偿。通过仿真,得到全差分放大器的差模增益为78.6 dB,乘法器可以实现两个信号的相乘,且应用该方法进行补偿的晶体振荡器的频率偏移为±2 ppm。

Exponential Voltage Generation Method for Crystal Oscillator Temperature Compensation

In order to obtain a more accurate clock source, the crystal oscillator was compensated to reduce the frequency variation with temperature. Compared with different temperature compensation methods of crystal oscillators, analog temperature compensation had higher performance. The focus of the analog temperature compensation circuit was to obtain the compensation voltage exponentially. This paper presented an analog multiplier method. Four MOSFETs were connected to the inputs of the fully differential amplifier. Combining the current-voltage relationship in the linear region multiplied the two analog signals. Different compensation voltages which were linear, quadratic, cubic, quadratic, and fifth power relationship with temperature would be generated. These voltages were superimposed by the summing circuit and could be used for high-order temperature compensation of the crystal oscillator. The differential mode gain of the fully differential amplifier was 78.6 dB, and the two inputs were multiplied by multiplier. Temperature stability of ±2 ppm deviation was achieved.