AD630 lock-in amplifier is an integrated preamplifier OPA627 and 4th-order ultra-low pass Butterworth filter, forming a set of minimum lock-in amplification system, which can detect and extract weak signals, and it can also be used in AD630 The modulation function.

When AD630 is used as a synchronous demodulator with a lock-in amplifier configuration, it can recover small signals from 100 dB interference noise (see the Lock-in Amplifier Application section). Chip channel bandwidth: 2 MHz, in actual use, it can be used for phase-locked amplification within 100K. AD630 can be regarded as a precision operational amplifier integrating two independent differential input stages and a precision comparator that can be used to select the active front end. The fast response time of this comparator and the high slew rate and fast settling time of linear amplifiers minimize switching distortion. After understanding the principle of phase lock, it can be replaced with an analog switch such as CD4052 when the accuracy is not high.

1. For the preamplifier, we use the OPA627 with low offset, low offset and precision operational amplifier. For the convenience of testing, only the magnification of OPA627 is set to 11 times (amplification of the same phase). In actual application, the resistance can be adjusted according to the signal amplitude to be detected to achieve a larger magnification, G=1+R2/R1.P
2. 6 is the synchronization signal input port. The synchronization signal is required to be a signal with the same frequency and phase with a detection signal. Since the module is powered by positive and negative, the signal input here must also be positive and negative. Here you can input a sine wave, triangle wave or square wave. Because of the internal comparator, it will eventually be converted to a square wave. But the required input amplitude needs to reach 200mvpp or more.D
3. 1 is the sync signal indicator, it will light up when the sync signal is input. When the sync signal frequency is low, you can see that the LED will flash with the sync signal frequency.P
4. 2 is the signal input port for balanced modulation, we will not introduce it here. P3 is the function selection terminal for phase-locked amplification and balanced modulation, and connections 1 and 3 are phase-locked amplification modes. Connections 2 and 3 are balanced modulation functions.I
5. f you choose to weld R9, if you dont weld R99, it will output directly without using the onboard filter. Welding R99, without welding R9, use the on-board filter output. Users can configure the filter parameters according to their needs. The default on-board is that the resistance is 10K, the capacitor is 1uF, and the low-pass cutoff frequency is about 30Hz.