Multifrequency Lockin Amplifier

The Multifrequency Lockin Amplifier (MLA™) from Intermodulation Products (also known as the Intermodulation Lockin Analyzer, ImLA™), is a unique measurement system which could be described as a synchronous multifrequency waveform generator, digital oscilloscope, and real-time Fourier analyzing instrument. It is constructed from precision, low distortion, analog components, high speed analog-to-digital (ADC) and digital-to-analog (DAC) converters, and a highly parallel logic circuit called a Field Programmable Gate Array (FPGA). Contact Intermodulation Products <> if you need help adapting the MLA with your experiment.

The MLA can run as many as 32 synchronous Lockins, ideal for frequency-domain multiplexing or simultaneous measurement of multifrequency linear response. But the MLA™ is particularly powerful for measuring nonlinear response in the form of intermodulation (response at the mixing products of multiple drive frequencies) or harmonics (response at integer multiples of a single drive frequency). The MLA™ can process 3 input triggers making possible triggered lockin measurement, where amplitude and phase is recorded in relation an external event, while avoiding transient distortions. It can also send three output triggers to initiate external events based on frequency domain response. With two output ports to drive the system under test and 4 input ports to monitor response, all synchronized to the same clock, the MLA™ is a multi-port, multi-frequency and multi-purpose measurement instrument.

This manual provides the basic information you need to use the MLA™. We start with a brief and general description of the ports. Subsequent sections describe how to use the MLA™ through its Graphical User Interface (GUI). Once you are familiar with the GUI you can start to program the instrument, controlling your measurement through a Python script. Full documentation on all functions needed to program the MLA™ is given in the section on MLA programming. For the experts, we have included sections describing Files Folders and Configurations, Calibration, details about the MLA™ Analog interfaces, and a discussion on Advanced Hardware and Software Topics.

connections MLA-3

Below we describe the third generation MLA™, the MLA-3. If you have an earlier 2nd generation MLA-2 see Connections MLA-2. The input and output ports of the MLA-3 are controlled in the Graphical User Interface (GUI) via the analog panel. This pannel has no function for the MLA-2.

All inputs and outputs are connected to the MLA™ through SMA connectors. The signal ground (outer shield of the SMA) is isolated from the metallic enclosure. This signal ground is connected to the ground planes on the PC board, and it is available from a banana connector on the back side.

When you measure (drive) single-ended, the voltage is between the center pin and the shield of the SMA connector labeled + (e.g. Input 1+ ). When you measure (drive) differential, the voltage is between center pins of two adjacent SMA connectors labeled + and - (e.g. Input 1+ and Input 1-). A complete description of the input and output ports including schematic diagrams is given in the section on Analog interfaces.


  • TRIGGER OUTPUT and TRIGGER INPUT The three input and three output triggers all respond to (send) the same voltage level, which can be set to 2.5 V, 3.3 V or 5.0 V with a jumper on the PC-board. The default factory setting is 5.0V unless otherwise specified when ordering.

  • AUX OUTPUT Four slow outputs with a combined speed of 800 kSam/sec. Output A is differential, whereas B,C, and D are single ended. These ports are controlled in the MLA GUI via the aux output panel.

  • OUTPUT Two high speed outputs (500 MSam/sec) with 16 bit resolution. These ports are are always differential. The MLA puts the output voltage between the + port and ground (SMA shield). A voltage of the opposite sign always appears between the - port and ground. If you use these ports differentially, the voltage difference between and + and - ports will be twice the set value. These ports are controlled in the MLA GUI via the analog panel.

  • INPUT Ports 1 and 2 are high-speed (250 MSam/sec) with 14 bit resolution. Ports 3 and 4 have moderate speed (50 MSam/sec) with 16 bit resolution. All ports have switchable range settings, AC or DC coupling, 50 ohm or 1M ohm input impedance. All ports can measure either differential or single-ended signals. When measuring single-ended the - input sees an open circuit (but the - input amplifier is grounded internally). These ports are controlled in the MLA GUI via the analog panel.


  • REF CLK OUT and REF CLK IN connections are used for synchronizing the internal clock of the MLA™ with the clock of some other piece of measurement equipment. These ports are designed to connect to a 50 Ohm matching impedance. REF CLK OUT sends a 10MHz square waveform, AC-coupled, voltage range 2 Vpp. REF CLK IN must be manually locked to an external reference (see hardware.Hardware.set_clkref_external_10MHz()). Other frequencies and voltage levels can be configured (see Clock Reference).

  • ETHERNET The MLA™ communicates with the computer via the Ethernet connection. The MLA™ may be directly connected to the Ethernet connection on the computer, or it may be be put behind an Ethernet router, switch or gateway.

  • SIGNAL GROUND gives external access to the grounding point for all input signals. This signal ground is isolated from the shielding enclosure (box) of the MLA™.

  • POWER 12 V DC is supplied to the MLA™ via an external power supply. Use only the power supply delivered from Intermodulation Products. Using any other supply voids the warranty.