The minimum time constant is 1 μs for LI5660/LI5655 (5 μs for LI5650/LI5645). Our newest lock-in amplifiers have achieved high-frequency and high speed response. 
 
This is an integer-period moving-average filter. Ripple caused by detection is greatly reduced, and the output is nearly settled in the averaging interval (integer period), so the time constant can be reduced (to obtain faster response).
 
It takes just about two cycles to lock on to the reference signal even at low frequencies. Furthermore, a moving average filter synchronized with the signal cycle obtains a high-speed response with a small ripple. 
 
Phase detection and subsequent processing are performed digitally. Output zero drift at high gains is smaller than the analog system, and up to 100 dB dynamic reserve can be obtained (measurement can be performed with a noise 100,000 times larger than the sensitivity, namely the signal full scale).
 
Time constant: 1µs (min.)
Frequency response: 11MHz(max.), 1mHz(min.)
Voltage measurement range: 10nV (min.)
Current measurement range: 10fA (min.)
Dual phases and Dual frequencies measurement
Built-in power supply to drive NF low noise amplifier
Built-in signal oscillator that can be used as a REF signal