JPH063447Y2 - Voltage / current generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a voltage / current generator, and in particular, an improved means for switching between voltage output and current output.

<Prior Art> Conventionally, in a voltage / current generating device, a voltage generating unit V and a current generating unit A are separately prepared as shown in FIG. 2, and the outputs of both units are switched by using a relay L. .

However, using two units of voltage and current in this way increases the number of parts, increases the mounting area, and is expensive.

<Problems to be solved by the proposal> The present invention was made to solve such problems. The purpose is to share a voltage / current output circuit to reduce the number of components and the mounting area. Thus, an inexpensive voltage / current generator is realized.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a feedback resistance of an operational amplifier to which an output of a digital-analog converter having a bipolar output configuration is applied to its inverting input terminal An inverting amplifier formed by connecting contacts is provided, voltage generating means for outputting the output of the inverting amplifier as an output voltage, and a shunt resistor connected in series to the switch by switching the switch to the other contact. And a voltage / current generating device is constituted by current generating means for taking out a current corresponding to the voltage generated in the shunt resistor as an output current. Hereinafter, examples will be described in detail.

<Embodiment> FIG. 1 is a circuit diagram of an embodiment of the voltage / current generator according to the present invention. In the figure, DAC is a digital-analog exchanger (hereinafter, simply referred to as DAC) having a bipolar output configuration, OP is an operational amplifier, Ri is an input resistance of the operational amplifier OP, Rf is a feedback resistance, and PB is a power booster. It is connected to the output terminal of the operational amplifier OP. The output terminal of the DAC is connected to the operational amplifier O via the resistor Ri.
It is connected to the inverting input terminal of P.

SW1 and SW2 are switches for switching between voltage output and current output, Rs is a shunt resistor, and H and L are output terminals. One end of the feedback resistor Rf is connected to the inverting input terminal of the operational amplifier OP, and the other end is connected to the output terminal of the power booster PB via the contact 1 of the switch SW1. One end of the shunt resistor Rs is connected to the contact 2 of the switch SW1, and the other end is connected to the common potential point. Both ends of the shunt resistor Rs are connected to the output terminal L via the switch SW2. Relays are used as the switches SW1 and SW2. The operation of the voltage / current generator having such a structure will be described below.

(B) Regarding voltage generation.

When a voltage is generated, the voltage Vr is output by the DAC, and the switches SW1 and SW2 are respectively connected to the contact 1 as shown in the drawing.
Connect to. As a result, the operational amplifier OP and the input resistance R
i, the feedback resistor Rf, and the power booster PB constitute an inverting amplifier whose gain is determined by the input resistor Ri and the feedback resistor Rf. As a result, the voltage Vo represented by the following formula (1) is taken out from the output terminals H and L. Vo =-
(Rf / Ri) · Vref (1) (b) Regarding current generation.

When a current is generated, the contacts of the switches SW1 and SW2 are connected to 2, respectively. When the voltage drop across the shunt resistor Rs when the load is connected to the output terminals H and L is Vr ⁻ , it is expressed by Vr ⁻ = − (Vr / Ri) · Rf. Here, when the output current and ^{Io, Io = - {(Vr} - / Rs) + (Vr / Ri)} Hence, Io = -Vr {(Rf / (Ri · Rs) + Rs / (Ri · Rs) } =-Vr (Rf + Rs) / (Ri.Rs) (2) That is, by connecting the contacts of the switches SW1 and SW2 to 2, the circuit including the resistors Ri and Rf becomes a constant current circuit, and the output current Io is This output current is supplied to the load connected to the terminals L and H via the switch SW2.

<Effects of the Present Invention> As described above, since the present invention shares the voltage output and current output circuits, it is an inexpensive voltage / current generator that reduces the number of parts and the mounting area. Can be realized. Moreover, by using a DAC having a bipolar output structure and skillfully using it, it is possible to obtain a device that does not require a relay for switching the polarity of the voltage / current output.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of the device according to the present invention, and FIG. 2 is a connection diagram of an example of a conventional device of this type. DAC ... Digital / analog converter, OP ... Operational amplifier, SW1, SW2 ... Switch, Rs ... Shunt resistance.

Claims (1)

[Scope of utility model registration request] 1. A digital-to-analog converter having a bipolar output structure, and an output of the digital-to-analog converter is formed by connecting one contact of a switch to a feedback resistor of an operational amplifier applied to an inverting input terminal thereof. The inverting amplifier has an inverting amplifier, the output of which is taken out as an output voltage, and a shunt resistor connected in series to the switch by switching the switch to the other contact. A voltage / current generator comprising: a current generator that takes out a current corresponding to a generated voltage as an output current.