JPH0760165B2 - Rectifier circuit - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to rectifier circuits, and more particularly to half-wave rectifier circuits.

[Conventional technology]

Conventionally, the circuit configuration of the half-wave rectifier generally uses either one-way characteristics of a diode or characteristics of a transistor base-emitter voltage and a collector current.

[Problems to be solved by the invention]

In the conventional half-wave rectifier described above, when using a diode, the input level needs to be equal to or higher than the forward voltage VF of the diode, and the forward voltage VF of the diode has a large temperature characteristic. The base-emitter voltage VBE has a large temperature characteristic,
The direct current amplification factor h _FE also has the drawback of having large temperature characteristics.

[Means for solving problems]

The rectifier circuit of the present invention comprises a differential amplifier consisting of two transistors having different transistor emitter sizes.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of claim 1 of the present invention.

In Fig. 1, the emitter sizes of transistors Q1 and Q2 are
It is 1: K. At this time, the transistor Q1, the respective collector currents I _c1 of Q2, I _c2 is the amplification factor of the transistor as _{α F Ic1 = αFIo / {1} + kexp (-V1 / VT)} Ic1 = αFIo / {1 + 1 / kexp (-V1 / VT)}. If, for example, k = exp 2 = 7.389 is set, a half-wave rectification characteristic is obtained by the collector current I _C2 of the transistor Q ₂ as shown in FIG.

FIG. 2 is a circuit diagram of another embodiment of the present invention. Input sensitivity can be lowered by inserting an emitter resistor in the differential pair.

For example, in FIG. 2, RE1 '= lRE1 is set.

At this time, V1 = -VTιnk {(αFI1) / Ic1-1} + (RE1 / αF) {(ι + 1) Ic1-ιαFI1} To put When γ = 0 Next to Substituting the formula into the formula, V1 = RE1I1 {(ι-1) / 2} -VTιnk At this time, if the tangent of I _C1 passes through the origin, then {VTιnk-RE1I1 (ι-1) / 2} / {(αFI1) / 2} = (4VT / αFI1) + (ι + 1) (RE1 / αF) ∴2VTιnk / αFI1)-{RE1 (ι-1)} / αF = (4VT / αFI1) + (ι + 1) (RE1 / αF) Therefore iRE1I1 = RE1'I1−2VT + VTιnk That is, a half-wave rectifier circuit with an improved input signal level can be obtained.

FIG. 3 is a circuit diagram showing still another embodiment of the present invention.

Now, let the emitter size of transistors Q _2i-1 and Q _{2i be} k _i : 1 and R
Let E _i ′ = l _i RE _i (i = 1, ..., n). Considering the same as the above description, if REi′Ii = −2VT + VTιnki, the collector currents of the transistors Q ₁ , ..., Q _2i-1 , ..., Q _2n-1 are constant current sources I ₁ ,. , I _i ,…, I _n all tangents at the point where α _F / 2 times passes the origin (V ₁ , I _Ci ) ＝ (0,0), and the value of I _Ci finally becomes V 1 becomes large. Saturates α _F
I _i .

That is, gi = Ii / {4VT + (RE + RE ') Ii} (i = 1, ..., n−
For 1) When you have a relationship The gain of each differential pair at input voltage V1 is It is twice as different.

Therefore Then, I ₁ is logarithmically approximated to the input voltage level V ₁ .

That is, the circuit shown in FIG. 3 provides a half-wave rectifier circuit having a logarithmic detection characteristic.

〔The invention's effect〕

As described above, the present invention can realize a rectifier circuit by forming a differential pair composed of two transistors having different transistor emitter sizes.

Moreover, a circuit that excels in temperature characteristics and operates up to a large input level can be realized with a small-scale circuit, and can be realized with a low power supply voltage. Moreover, it is possible to have a logarithmic characteristic and the effect is great.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, FIG. 3 is a circuit diagram showing still another embodiment of the present invention, and FIG. FIG. 4 is a diagram showing characteristics of the circuit of FIG. 1.

Claims (3)

[Claims] 1. A differential pair is formed by two transistors having an emitter size of 1: k (k> 1), an input signal is provided between the bases of the two transistors, and a transistor having an emitter size of k times is used. A rectifier circuit for obtaining a half-wave rectified output for the input signal from a collector. 2. The rectifier circuit according to claim 1, wherein each of the two transistors has an emitter resistance. 3. A differential amplifier having two transistors each having an emitter size of 1: k (k> 1), each of the two transistors having an emitter resistance, and n differential amplifiers in parallel. Connected, the product REiIi of the emitter resistance REi (i = 1, ..., n) and the size Ii (i = 1, ..., n) of the constant current source of the differential amplifier becomes REIiIi = 2VT. Relationship and ρi = 4 / (ki + 1 / ki + 2) ρi (i = 1, ..., n) is for constant a A rectifier circuit having a relationship of (i = 1, ..., N-1). However, VT = kT / q