JPH0783216B2 - Half-wave rectifier - Google Patents

Description

The present invention relates to a MOS type integrated circuit, and more particularly to a half-wave rectifier in a MOS type integrated circuit.

[Conventional technology]

Conventionally, in order to form a half-wave rectifier on this type of MOS integrated circuit, there is a half-wave rectifier composed of, for example, a switched capacitor circuit. (Eg PE Allen and E. Sanc
hex Sine−ncio: “Switched capacitor circu−its” Van
Nostrand Reinhold Co (1984)).

[Problems to be solved by the invention]

The above-mentioned conventional half-wave rectifier has a drawback that the circuit scale becomes large.

In contrast to the conventional half-wave rectifier circuit described above, the present invention has an original content that it can be configured by a pair of differential pairs that are out of balance in a MOS integrated circuit.

[Means for solving problems]

The half-wave rectifier of the present invention has a differential pair made up of two transistors having different gate width and gate length ratios.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, M1 and M2 are N-channel transistors, and I
_SS indicates a constant current source. Then, the ratios of the gate width and the gate length of the transistors M1 and M2 are set to W1 / L1 and W2 / L2, respectively, and (W2 / L2) / (W1 / L1) = k (≠ 1) (1). The generality is not lost even if k> 1 is considered here.

Set the drain currents of the transistors M1 and M2 to I _d1
And I _d2 and the gate voltages are V _gs1 and V _gs2 , I _d1 = α (V _gs1 −V _t ) ² (2) I _d2 = kα (V _gs2 −V _t ) ² (3) where V _t is a transistor It is the threshold voltage of M1 and M2, and α is a constant determined by the device parameter of the transistor.

Also, I _d1 + I _d2 = I _ss (4) V _gs1 −V _gs2 = ΔVi (5).

From equations (1) to (5) Is required. In equation (6), the third term As shown in FIG. 2, ΔVi = 0 with respect to the input signal ΔVi.
It is known that the curve becomes a point symmetric with respect to the point. On the other hand, in the first term Shows a quadratic curve with respect to the input signal ΔVi, as shown in FIG. Of the second term Can be considered as the y-intercept of the quadratic curve of the first term.

Therefore, when k is increased as shown in FIG.
The characteristics of I _d1 is also small values of I _d1 in the negative input with inclination becomes progressively smaller, it can be seen that with a half-wave rectification characteristic. On the other hand, since the characteristic of I _d2 is the differential output of I _d1 , it also has a half-wave rectification characteristic.

That is, the drain current of the transistor M2 can be monitored by the current mirror circuit composed of the transistors M3 and M4 as shown in FIG. Here, if a resistor R1 is connected to the output of the current mirror circuit, the current output can be converted into a voltage.

Figure 3 shows ΔVi-I _d1 simulated with k = 10.
The characteristic of Id ₁ when the input signal ΔVi is a sine wave based on the characteristic is shown with respect to the time axis t.

FIG. 4 is a circuit diagram of the second embodiment of the present invention. M1 and M2 are transistors, R1 is a resistor, C1 is a capacitor, I _SS
Is a constant current source, ΔVi is an input signal, and AC signal V _DD is a power supply voltage. At this time, the DC output voltage V _{0 with} respect to the AC input signal ΔVi becomes as shown in FIG.

〔The invention's effect〕

As described above, the present invention has an effect of realizing a half-wave rectifier by forming a differential pair with two transistors having different gate width and gate length ratios.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a characteristic diagram of FIG. 1, FIG. 3 is a simulation value when k = 10 in FIG. 1, and FIG. FIG. 5 is a circuit diagram showing a second embodiment of the present invention, and FIG. 5 is a characteristic diagram of FIG. M1, M2, M3, M4 …… Transistor, R1 …… Resistor, C1 …… Capacitor, I _SS …… Constant current source.

Claims (1)

[Claims] 1. A constant current drive, wherein the ratio (W / L) of the gate width (W) and the gate length (L) of the transistor is different from each other.
A half-wave rectifier comprising a differential pair composed of two transistors, wherein a signal is input between two gates constituting the differential pair and a drain current is output.