MPY634: Can I use MPY634 about frequency range 1.6Khz~0.1Hz?

There is no minimum frequency. You can extrapolate from the typical performance curves.

Please note that using an analog multiplier is quite unusual nowadays. Wikipedia says:

In most cases, the functions performed by an analog multiplier may be performed better and at lower cost using digital signal processing techniques. At low frequencies, a digital solution is cheaper and more effective and allows the circuit function to be modified in firmware. As frequencies rise, the cost of implementing digital solutions increases much more steeply than for analog solutions. As digital technology advances, the use of analog multipliers tends to be ever more marginalized towards higher-frequency circuits or very specialized applications.

In addition, most signals are now destined to become digitized sooner or later in the signal path, and if at all possible the functions that would require a multiplier tend to be moved to the digital side. For example, in early digital multimeters, true RMS functions were provided by external analog multiplier circuits. Nowadays (with the exception of high-frequency measurements) the tendency is to increase the sampling rate of the ADC in order to digitize the input signal allowing RMS and a whole range of other functions to be carried out by a digital processor. However, blindly digitizing the signal as early in the signal path as possible costs unreasonable amounts of power due to the need for high-speed ADCs. A much more efficient solution involves analog preprocessing to condition the signal and reduce its bandwidth so that energy is spent to digitize only the bandwidth that contains useful information.

In addition, digitally controlled resistors allow microcontrollers to implement many functions such as tone control and AGC without having to process the digitized signal directly.

Please tell us what is the actual problem that you're trying to solve.

Hi Hoonmin,

Yes, I will confirm that the MPY634 can be used at this frequency range. It can be used from DC up to the frequencies specified in the datasheet.