JPH0216607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rectifier circuit that can be used for signal processing in, for example, a noise reduction system.

[Technical background of the invention and its problems]

Conventionally, rectification within semiconductor circuits has generally been performed using diodes. The rectifying characteristics of a diode are mainly determined by its semiconductor material, so in order to obtain the desired characteristics, it is necessary to select the semiconductor material appropriately or use a diode that has undergone special processes such as gold diffusion. It was hot.

However, the conventional rectifier circuit can be directly used as an IC.
It is not easy to become This is because it is technically difficult to make diodes on an IC substrate using a semiconductor material different from that of the substrate, or a diode using a special process, and is not suitable for mass production. In other words, the rectifier circuit built into the IC
From the viewpoint of productivity, it is required to use a diode made of the same semiconductor material as the substrate and without any special process. For this reason, when converting a discrete circuit into an IC, the circuit configuration had to be reconsidered in order to obtain the desired rectification characteristics.

[Purpose of the invention]

The present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a rectifier circuit that can be incorporated into an IC and that can easily obtain desired rectification characteristics.

[Summary of the invention]

By connecting a differential amplifier and a diode in parallel, and rectifying the low voltage region with the differential amplifier and rectifying the high voltage region with the diode, a rectifier circuit having desired rectification characteristics is obtained.

[Embodiments of the invention]

A first embodiment of the invention is shown in FIG. The resistors 9 and 10 are connected in parallel to a power source 11 having a potential of Vcc. The emitters of PNP transistors 7 and 8 are connected in series to these resistors 9 and 10, respectively. The base of transistor 8 is connected to the base and collector of transistor 7. That is, transistors 7 and 8 constitute a current mirror.

The collector of the transistor 7 is connected to the collectors of the NPN transistors 2 and 3. The base of the transistor 2 is connected to the input terminal 1, and the emitter is connected to the base of the transistor 3. Here, transistors 2 and 3 are first amplifiers, and they constitute a Darlington circuit.

The collector of the NPN transistor 4 is the power supply 11
The base is connected to the collector of transistor 8, and the emitter is connected to the emitter of transistor 3. This transistor 4 is the second amplifier. It is assumed that transistors 2, 3, and 4 have the same characteristics, and their amplification factor is β. Between the emitters of transistors 3 and 4 and ground 6,
A constant current source 5 through which a constant current I ₀ flows is provided. Collector of transistor 8 and output terminal 1
A resistor 12 is connected between the resistor 3 and the resistor 3. Furthermore, a resistor 15 is connected between the output terminal 13 and a reference power source 16 having a potential of Vref.
The above transistors 2, 3, 4, 7, 8, resistors 9, 10, 12, 15, constant current source 5, power supply 11,
The ground 6 and the reference power supply 16 constitute a differential amplifier.

A diode is connected between the input terminal 1 and the output terminal 13. That is, a differential amplifier and a diode are connected in parallel between the input terminal 1 and the output terminal 13.

Next, the operation of this circuit will be explained. The sum of the collector currents of transistors 2 and 3 is i ₀ , the current flowing through resistor 12 is i ₁ , and the current flowing through diode 14 is
i ₂ , and the potential difference between input terminal 1 and output terminal 13 is assumed to be Vf. Also, for simplicity, it is assumed that Vcc=10v and Vref=5v. If the mirror ratio of the current mirror made up of transistors 7 and 8 is 1:N, then the collector current of transistor 8 is N×i ₀ . If β is sufficiently large, the base current of transistor 4 can be ignored and it can be considered that i ₁ =N×i ₀ . Furthermore, since the collector current of transistor 2 is approximately the base current of transistor 3, the collector current of transistor 3 can be considered to be equal to i ₀ .

Base-emitter voltage V _BE3 of transistor 3
It is well known that can be expressed as V _BE3 =V _T · _lo i ₀ /I _S1 .
However, V _T is a thermal voltage, and if k is the Boltzmann constant, q is the electronic charge, and T is the absolute temperature, V _T =k _T /q. Further, I _S1 is the saturation current of the transistor 3. Similarly, the base-emitter voltages V _BE2 and V _BE4 of transistors 2 and 4 are V _BE2 = V _T・lo _{i 0} /β/I _S1 , V _BE4 = V _{T ・}lo I ₀ −i ₀ /I _S1 It can be expressed as From this, V _f is the resistance 1
If the resistance value of 2 is R ₁₂ , then V _f =V _BE2 +V _BE3 −V _BE4 +i ₁・R ₁₂ =V _T・l _o i ₀ /β/I _S1 +V _T・l _o i ₀ /I _S1 −V It can be written as _T・_lo I ₀ −i ₀ /I _S1 +i ₁・R ₁₂ =V _T・_lo (i _1/N ) ² /(I ₀ −i _1/N )βI _S1 +i ₁・R ₁₂ .

On the other hand, the relationship between V _f and i ₂ can be expressed by the following equation.

V _f =V _T · _lo i ₂ /I _S2 where I _S2 is the saturation current of the diode 14.
If the sum of i ₁ and i ₂ is i _f , then the relationship between V _f and i _f represents the rectification characteristics of this rectifier circuit.

As can be seen from these equations, the V _f −i _f characteristic is
It has variables such as mirror ratio, I ₀ , β, I _S1 , I _S2 , and R ₁₂ . That is, by appropriately selecting these variables, desired rectification characteristics can be obtained.

Now, for example, I ₀ = 27 μA, β = 100, I _S1 = I _S2 =
2.5×10 ^-16 A, N=1, T=300K, R ₁₂ =2KΩ,
The resistance values of resistors 9, 10, and 15 are 2KΩ, 2KΩ,
Assuming 1MΩ, the relationship between V _f and i ₁ , i ₂ , and i _f is as shown in Figure 2. In the region where V _f is small, i ₁ is larger than i ₂ and the amplifier circuit mainly performs rectification. However, i ₁ is almost saturated around V _f =0.7V. Instead, i ₂ rises from around V _f =0.6V and increases rapidly. In other words, in a region where V _f is large, the diode mainly performs rectification.

In this way, in the case of only a diode, the only way to change its rectification characteristics is to change I _S2 .
Although it is difficult to obtain desired characteristics, according to this embodiment, desired characteristics can be easily obtained by changing I ₀ , mirror ratio, β, R ₁₂ and the like.

The second and third embodiments are shown in FIGS. 3 and 4, respectively. First, in the embodiment shown in FIG. 3, each of the transistors 2 and 4 in the first embodiment is replaced with a Darlington circuit composed of transistors 19, 20 and 21, 22 having the same characteristics as these, and β When using a transistor whose current is not very large, that is, when using the circuit shown in the first embodiment, good rectification characteristics can be obtained even when the base current of the transistor 4 cannot be ignored. The embodiment shown in FIG. 4 replaces the transistor 20 in FIG. 3 with a diode 23, and, like the second embodiment, is effective when using a transistor whose β is not very large.

In the above embodiment, the characteristics of the transistors 2, 3, 4, 19, 20, 21, and 22 are the same, but transistors with different characteristics may be used.

〔Effect of the invention〕

According to the present invention, a rectifier circuit having desired rectification characteristics can be easily obtained by changing the configuration of the differential amplifier, the mirror ratio of the current mirror, etc.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention,
Figure 2 is a rectification characteristic diagram of the circuit shown in Figure 1;
4 are circuit diagrams showing the second and third embodiments, respectively. 1...Input terminal, 13...Output terminal, 2, 3,
4, 7, 8...transistor, 5...constant current source,
14...Diode, 6,11...Power supply.

Claims (1)

[Scope of Claims] 1. A current mirror having first and second power supplies, first and second terminals, and a power supply terminal, the power supply terminal being connected to the first power supply; a first amplifier having a collector connected to a first terminal and a base connected to an input terminal; and a second amplifier having a collector connected to the first power supply terminal and a base connected to the second terminal. an amplifier; an output terminal connected to the second terminal; a constant current source provided in common between the first and second amplifiers and the second power source; the input terminal; A rectifier circuit comprising a diode provided between the output terminals. 2. The rectifier circuit according to claim 1, wherein a resistor is inserted between the second terminal and the output terminal. 3. The rectifier circuit according to claim 1A, wherein the first amplifier comprises a plurality of transistors having a Darlington circuit configuration. 4. The rectifier circuit according to claim 1A, wherein the second amplifier comprises a plurality of transistors having a Darlington circuit configuration. 5 Between the first power source and the power terminal,
The rectifier circuit according to claim 1A, characterized in that a resistance element is connected.