JPH07105662B2 - Multi-function differential amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a multifunctional differential amplifier used in, for example, a frequency converter or the like.

(Conventional example) Generally, a frequency converter is often used for signal processing of electronic devices. The frequency converter shown in FIG.
and Design of Analog Integrated Circuit (JOHN WIL
EY & SONS) "(Analysis and Design of Analog Integrated Circuit (John Wiley and Sons)), pages 570-575.

In FIG. 6, the transistors Q1 to Q6 constitute a double balanced type differential amplifier, and the differential amplifier section D11 in the lower stage is a constant current source I.
Driven by ₀ , the input signal Vin is supplied between the bases of the pair of transistors Q5 and Q6. Therefore, the transistor Q
The signals at the bases of Q5 and Q6 have opposite phases. Upper differential amplifier
D12 and D13 are driven by the transistors Q5 and Q6, respectively, and an input signal Ain is applied between the common bases of the transistors Q1 and Q4 and the common bases of the transistors Q2 and Q3 that form the differential amplifiers D12 and D13. Supplied. Therefore, the signals of the common bases of the transistors Q1 and Q4 and the signals of the common bases of the transistors Q2 and Q3 have opposite phases. Transistor Q
The collectors of 1, Q3 are connected to the power supply line 1 via the resistor R1, and the collectors of the transistors Q2, Q4 are connected to the power supply line 1 via the resistor R2.

In the above circuit, the transistors Q2 and Q3 are turned off when the transistors Q1 and Q4 are turned on, and the transistors Q2 and Q3 are turned on when the transistors Q1 and Q4 are turned off. As described above, by controlling the transistors Q1 to Q4 by the input signal Ain, the current flowing through the resistor R2 is changed to the collector current I _C5 of the transistor Q5 and the collector current I _{C6 of the} transistor Q6.
Alternating to and.

Now, when a signal as shown in FIG. 7 (a) is supplied between the input parts v1 and v2 and a signal as shown in FIG. 7 (b) is supplied between the input parts a1 and a2, the output part 2 is supplied. Obtains the frequency conversion output as shown in FIG. 7 (c).

(Problems to be Solved by the Invention) According to the circuit described above, since the transistor is connected to overlap between the power supply and the ground, there is a problem that the dynamic range becomes narrower as the power supply voltage becomes lower.

Therefore, an object of the present invention is to obtain a multifunctional differential amplifier which can be driven at a low voltage and can obtain a sufficient dynamic range.

[Structure of Invention]

(Means for Solving Problems) In the present invention, as shown in FIG.
Each differential amplification section D1 ~ D4 and each constant power source I1 ~ I4,
Make one pair between the power supply and ground. Then, the first and second signals are combined and supplied to the differential input section of each differential amplifier section.

(Operation) With the above configuration, the multiplication result of the first and second signals can be obtained with low voltage driving and with a sufficient dynamic range.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows an embodiment of the present invention, in which the first signal input section x1, x
The first signal Xin is supplied between the two, and the second signal input section
A second signal Yin is supplied between y1 and y2.

One input part y1 of the second signal is connected to the base of the transistor Q2 which constitutes the first differential amplification part D1 and the second differential amplification part.
It is connected to the base of a transistor Q3 that constitutes D2. The other input part y2 is connected to the base of the transistor Q6 that constitutes the third differential amplifier D3 and the base of the transistor Q7 that constitutes the fourth differential amplifier D4. One input part x1 of the first signal is connected to the base of the transistor Q1 that forms the first differential amplification section D1 and the base of the transistor Q8 that forms the fourth differential amplification section D4. Input part x2
Is the base of the transistor Q4 that forms the second differential amplification section D2 and the transistor Q5 that forms the third differential amplification section D3.
Connected to the base of.

Constant current sources I1 and I2 are connected between the common emitters of the transistors Q1 and Q2 and the ground, and between the common emitters of the transistors Q3 and Q4 and the ground, and a resistor R3 is connected between the common emitters. Constant current sources I3 and I4 are connected between the common emitters of the transistors Q5 and Q6 and the ground, and between the common emitters of the transistors Q7 and Q8 and the ground, and a resistor R4 is connected between the common emitters.

Therefore, the first and second differential amplifiers D1 and D2 are driven by the common constant current circuit 11, and the third and fourth differential amplifiers D3 and D4 are driven by the common constant current circuit 12. Will be done.

Next, the collectors of the transistors Q1 and Q5 are commonly connected to the resistor R1.
Connected to the power supply line 13 via the transistor Q4, Q8
The collectors of are commonly connected to the power supply line 13 via the resistor R2. The collectors of the other transistors Q2, Q3, Q6, Q7 are connected to the power supply line 13.

In the above circuit, assuming that the transistors Q1, Q4, Q6, Q7 are on, the transistors Q2, Q3, Q5, Q8 will be off in the case of complete switching operation. In this state, the current flowing through the resistor R2 becomes the collector current I _C4 of the transistor Q4. At this time, transistors Q1 and Q4
The resistors R1, R2, R3 and the constant current sources I ₁ , I ₂ operate as a differential amplifier circuit, and the signal Xin supplied between the input parts x1, x2 is amplified by this amplifier circuit. Conversely, when the transistors Q2, Q3, Q5, Q8 are on, the current flowing through the resistor R2 is
It becomes the current I _C8 flowing in the collector of. At this time, the transistors Q5 and Q8 and the resistors R1, R4, I3, and I4 operate as a differential amplifier circuit, and the signal supplied between the input parts x1 and x2 is amplified by this amplifier circuit. Where clock pulse φ,
Is supplied to the input sections y1 and y2, and the low frequency signal Xin to be frequency-converted is supplied to the input sections x1 and x2, the above circuit operates as a frequency converter. Now, constant current sources I1, I
If the currents flowing through 2, I3 and I4 are equal, the resistors R3 and R4 are equal, and all the transistors have the same size, the frequency-converted output can be obtained as shown in FIG.

FIG. 2 shows another embodiment of the present invention. In this example, the collectors of the transistors Q1, Q2, Q5, Q6 are connected to the power supply line 13 via the resistor R1, and the transistors Q3, Q4, Q7, Q8 are connected.
Is connected to the power supply line 13 via the resistor R2. This circuit lowers the DC voltage operating point of the output section as compared with the previous embodiment. The operation is the same as in the previous embodiment, so the explanation is omitted.

In the above description, the circuit of the present invention has been described as functioning as a frequency converter, but the circuit can be used as various processing circuits.

FIG. 3 (a) is an example in which a current mirror circuit including transistors Q10 and Q11 is connected to the output section and used as a phase comparator. By supplying the signals Xin and Yin shown in FIG. 6B between the input parts x1 and x2 and between the input parts y1 and y2, an output showing a phase error at the part where the phases of the two signals Xin and Yin do not match is output. It is possible to obtain a comparison circuit having a very high detection efficiency.

Further, the circuit of the present invention can be used as a gain switching circuit. For example, in FIG. 1, the values of the resistors R3 and R4 are set to be different, and input is made so as to select the output of either the group of the differential amplifiers D1 and D2 or the group of the differential amplifiers D3 and D4. If a bias is applied to the parts y1 and y2, outputs with different gains can be obtained.

When R3 ≠ R4, the gain G is r _e ; It becomes the internal resistance of the transistor.

Furthermore, the circuit of the present invention can also be used as a full-wave rectifier circuit. FIG. 5 shows the signal Xin supplied between the input parts x1 and x2 and the signal Yin supplied between the input parts y1 and y2 in this case.
And the signal appearing at the output. This example
This is an example in which the circuit of FIG. 1 is used as it is. Although the above-mentioned embodiments have been described using the bipolar transistor,
Not limited to this, the same effect can be obtained by using a MOS type transistor or the like.

〔The invention's effect〕

As described above, according to the present invention, there is provided a multifunctional differential amplifier which has a small number of stacked transistors existing between a power supply and a ground, can be driven at a low voltage, and can obtain a wide dynamic range at the output. Can be provided.

[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, and FIG. 3 is a circuit diagram showing still another embodiment of the present invention and this circuit. 4 and 5 are signal waveform diagrams for explaining the use of the circuit of the present invention, and FIG. 6 is a circuit diagram showing a conventional frequency converter. FIG. 7 is a signal waveform diagram for explaining the operation of the circuit of FIG. Q1 to Q8, Q10, Q11 …… transistors, I1 to I4 …… constant current sources

Claims (1)

[Claims] 1. A first differential amplifier, a second differential amplifier, a third differential amplifier, and a fourth differential amplifier each having a signal input portion provided on an input electrode of a pair of transistors, and the first differential amplifier and the second differential amplifier. Common input section on each side,
A first signal input section for supplying a first input signal between one common input section of each of the third and fourth differential amplifiers; and a common of the other one of the first and fourth differential amplifiers. Input part,
A second signal input section that supplies a second input signal between the other common input sections of the second and third differential amplifiers, and the first and second differential amplifiers are commonly driven. Constant current source for driving, a second constant current source for commonly driving the third and fourth differential amplifiers, and a common connection output end of the first and third differential amplifiers A first load connected between the power supply and a power supply; a second load connected between the common connection output terminals of the second and fourth differential amplifiers and a power supply; the first load or the second load; And a signal output terminal for extracting an output signal from at least one output terminal of the common connection output terminals to which a load is connected.