News Release

New Product
January 18, 2021

NJR has begun to provide samples of excitation amplifier NJU7870
for automotive resolvers developed with TAMAGAWA SEIKI

 New Japan Radio (NJR) has newly developed a low-voltage drive resolver (angle senor) excitation amplifier NJU7870 and begun to provide samples. The excitation amplifier is used to detect the rotation angle of motor shafts and rotating shafts in hybrid cars and electric cars.
 The NJU7870 realizes easy design of resolver excitation circuit, miniaturization of mounting board and ECU*1, weight saving and improvement of reliability.

General Description

 High precision angle detection and high safety are required for drive motors in eco-friendly cars such as hybrid cars and electric cars, so the resolvers (angle sensors) that are used to detect the angle of drive shafts and rotating shafts play an important role.
 The resolver system requires an R/D converter that converts the detected resolver signal into a digital signal and an excitation circuit that outputs an excitation signal to the resolver.
 NJR has developed the resolver excitation amplifier NJU7870 as a high performance resolver system with TAMAGAWA SEIKI that has a high market share and market performance in resolvers and R/D converters.

*1 ECU : Electronic Control Unit


    • 1. The excitation circuit of voltage input and current output that is suitable for resolver excitation reduces the design time.
      •  In the conventional discrete configuration, when configuring an excitation circuit of voltage input and current output (current control mode), there are some problems such as the complexity of circuit design increases since the resolver is an L load, and simple calculation and measurement are not matching, so it took a lot of design effort to obtain the desired characteristics.
         The NJU7870 integrates the excitation circuits of differential voltage input and differential current output and achieves optimum circuit characteristics for resolver driving.
         It is a very simply and easy-to-use IC that only inputs a differential voltage signal according to the desired current amplitude, and it contributes to a significant reduction in design time that has been a problem in the conventional discrete circuit design.


NJU7870 Excitation Circuit (Configuration of differential voltage input, differential current output)

    • 2. Supports a wide range of resolver systems by 2 excitation circuits
      •  Furthermore, the NJU7870 equipped 2 circuits of differential voltage input and differential current output. It is possible to control each circuit from the external input, and combine with various resolver systems such as 1-phase excitation or 2-phase excitation.
         In addition, the NJU7870 achieves high precision performance matching for each phase that has been difficult to achieve with a discrete configuration. It contributes to higher performance motor angle detection in a 2-phase excitation resolver system.

Circuit configuration example

2-phase excitation 2-phase output
1-phase excitation 2-phase output
  • 3. Integrates into the small package SSOP16, realizes miniaturization of the board with the minimum external components
    •  The NJU7870 adopts the small package SSOP16, and the external parts are only the capacitor connected to the power supply. It contributes to a significant reduction in mounting area compared with the conventional discrete circuit configuration. (90% reduction compared with the conventional discrete circuit configuration: our research)
NJU7870(SSOP16: 5.0×6.4×1.2mm)

Discrete circuit configuration and NJU7870 package size


  • Operating voltage (2.4V to 5.5V)
  • Differential voltage input and differential current output
  • Transconductance (13.5mAP/VPP typ.)

  • Operating temperature range (Topr= -40ºC to +125ºC)
  • Operating current (4mA typ.)
  • Built-in thermal shutdown circuit
  • Built-in external control shutdown function
  • Package (SSOP16)


  • Angle Detection Sensor (resolver excitation circuit)



Samples and Schedule

  • SamplesProviding
  • ScheduleMass production from April, 2021

These contents of a release are the information as of an announcement date. Please contact us about the latest information.

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