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  • DOS series | Bipolar power supply (Low Voltage Amplifiers) | Matsusada Precision
  • DOS series | Bipolar power supply (Low Voltage Amplifiers) | Matsusada Precision

Fast Response
Four-Quadrant Bipolar Power Amplifier

  • Voltage range:
    ±20V to ±60V
  • Current:
    ±2.5A to ±100A
  • Power:
    150W to 2000W
  • Fast response:
    DC to 200kHz

Fast response four-quadrant bipolar power amplifier

DOS series is four-quadrant bipolar power supply with high-speed response of DC to 200 kHz (CV mode). It shall output various waveforms including sinusoidal, triangular, saw-tooth, rectangular, and more with combination with a function generator. As the DOS series amplifies any waveform, it is suitable for all sorts of simulation tests.
Sourcing and sinking of electrical power with four-quadrant operation as well as 2 operation modes of CV and CC are possible. Compact size for such various functions and ultra high-speed response power supply. In addition, the features of large meters with high visibility and superior operability make the DOS series versatile four quadrants bipolar power supply which can be used on a wide variety of occasions from in the laboratory to the production line.

Note: This product is not designed for charge and discharge of battery.
For battery charging and discharging applications, please refer to the Battery Cycle Tester product page.


Fast response
Suitable for transient response test because of its ultra-high-speed response DC to 200 kHz and high power, maximum 2000 W.
Four-quadrant action
DOS series can be used both as a high speed response DC power supply and as a DC electronic load.
DC bias
10-turn potentiometer to be used as the output setting volume when used as the DC power supply and as the bias setting dial at outputting AC waveform is equipped.
Constant Voltage (CV)/Constant Current (CC)
A single switch selects between CV and CC modes.
Compact & Lightweight
For maximum compactness and lightweight, the DOS series has been improved for small footprint and handiness.
DC output meter equipped
3-digit digital meter displays the DC value of the output voltage and current. (The option of rms indication is available.)
Complete protective functions
Protective functions against overvoltage/overcurrent and against output short-circuit are completely provided.
Master/Slave control (option) for more power requirement. Both of Master unit and Slave unit are usable as the individual amplifier. (Frequency response will vary in case of master/slave operation, please ask sales staff.)


  • Inductive load such as coil and transformer
  • Various motor tests
  • Evaluation test for solar panel related devices
  • Ripple test of capacitors
  • Voltage regulation tests for in-vehicle electrical component
  • For surface treatment


* Models with voltage, current or frequencies not listed here are also available. Please contact the nearest sales office.

Model Maximum output
Voltage Current Power
DOS20-7.5 ±20 V ±7.5 A 150 W
DOS20-15 ±20 V ±15 A 300 W
DOS20-30 ±20 V ±30 A 600 W
DOS20-60 ±20 V ±60 A 1200 W
DOS20-100 ±20 V ±100 A 2000 W
DOS25-6 ±25 V ±6 A 150 W
DOS25-12 ±25 V ±12 A 300 W
DOS25-24 ±25 V ±24 A 600 W
DOS25-48 ±25 V ±48 A 1200 W
DOS25-80 ±25 V ±80 A 2000 W
DOS45-3.3 ±45 V ±3.3 A 150 W
DOS45-6.6 ±45 V ±6.6 A 300 W
DOS45-13.3 ±45 V ±13.3 A 600 W
DOS45-16 ±45 V ±16 A 720 W
DOS45-26.7 ±45 V ±26.7 A 1200 W
DOS45-44.4 ±45 V ±44.4 A 2000 W
DOS60-2.5 ±60 V ±2.5 A 150 W
DOS60-5 ±60 V ±5 A 300 W
DOS60-10 ±60 V ±10 A 600 W
DOS60-20 ±60 V ±20 A 1200 W
DOS60-33.3 ±60 V ±33.3 A 2000 W


Protective Functions

Overvoltage protection (OVP)

DOS series is equipped with overvoltage protection, which protects load by limiting voltage up to approx. 110% of the rated output voltage even at abnormal conditions.

* It is possible to set variable 0% to approx. 110% output voltage range with -LVc option.

Overcurrent protection (OCP)

DOS series is also equipped with overcurrent protection, which protects power supplies and load by limiting current up to approx. 110 % of the rated output current.

* It is possible to set variable 0% to approx. 110% output voltage range with -LCc option.

High speed overcurrent protection

DOS series is provided with 2 types of overcurrent protection, high-speed overcurrent protection to limit the pulse current, and standard overcurrent protection to limit the static current. The standard overcurrent protection limits the static current, responding at around 1 msec. Additional high-speed overcurrent protection can limit the pulse current of square waveforms or from a capacitive load at approximately 2 times rated current.

High speed overcurrent protection

Output Range

DOS series is a bipolar power supply which can perform four quadrant operation. They can supply (source) and absorb (sink) current in the field of the drawing on the right.

Output range

Characteristic of Amplifier

Rise time

(Stepping time): The response time is sometimes described by the rise time (as shown in the drawing on the right).
The rise time of an amplifier at a response speed of (= frequency bandwidth) Fc (Hz) is generally acquired by "tr ≒ 0.35/fc."
Fall time tf is the same as tr.
Frequency bandwidth: at 200 kHz or lower, tr = tf = around 1.8 μs, at 100 kHz or lower, tr = tf = around 3.5 μs

Rise time

Response speed

When accurate output waveforms are required, select an amplifier with a frequency bandwidth higher enough than the operating frequency.
In the case of using sine waves, 3 to 5 times more frequency bandwidth is required, and around 10 times more in the case of square waves in general.
Inadequate bandwidth causes not only a decrease in the output amplitude but much difference between the input and output phases. Therefore operating the product while monitoring the actual output waveforms is recommended.

Response speed

Inductive load

Some inductance of inductive load may cause resonance in CC mode.
In such cases, connect a C-R series circuit between output terminals to prevent resonance.

Capacitive Load

When a capacitive load is more than 100 pF (including a stray capacitance of output wire), the resonance in the output may occur. In that case, install 100-ohm (@0.1 μF) to 1000-ohm (@1000 pF) of high voltage resistance in the output in series. Please note that the frequency band will be limited as the formula written in the right figure when an amplifier is used with a capacitive load.
In addition, when an amplifier is used for the user, such as a corona discharge, the current which is higher than the rating will flow, and it will affect the amplifier badly. In this case, as well as the time to use an amplifier with a capacitive load, please install the output resistance and limit the current.

* Please avoid continuous inputting of a high-frequency signal which reduces the output frequency of an amplifier. An amplifier will be broken because of an increase in internal loss.

This image explains frequency band when a capacitive load is connected.

Read more


For details, download the datasheet below.



Output current limit

Variable from 0 to approx. 110% with the dial on the front panel

Floating ground (withstand voltage 200 Vdc)

-LMsm, -LMss

Master/Slave control (parallel operation)

Maximum 3 units including master unit are hooked. "-LMsm" for the master unit and "-LMss" for slave units.
Please order the required number of units. Every master and slave unit is exclusive use, but it can also be operated independently.
If you want to change the master-slave combination, it will need to be readjusted at our factory.

Automatic output recovery (previous: no power failure protection)

This option retains the output state when recovering from an input power interruption, such as an AC power switch ON/OFF or a power failure. Therefore, there is no need to reset the protection status by turning off the OUTPUT switch once.
Caution: If you turn on the power while the OUTPUT setting is ON, the output will be ON.

rms display


Output voltage limit

Variable from 0 to approx. 110% with the dial on the front panel

200 Vac to 240 Vac ±10% single phase, 50 Hz/60 Hz input

(150 W and 300 W models only)

How to Order

When ordering, add Option No. in the following order by alphabet and input voltage to Model No.
[Example] DOS25-12-LCcDFMsmNPrSVc(220V)


Function Generator


For details, download the datasheet below.


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