JPS60163511A - High frequency amplifier circuit - Google Patents

Abstract

PURPOSE:To attain amplification of high band with a stable gain by performing high frequency amplification with a current mirror circuit where the emitter size of each element is matched to a desired gain after a voltage signal to be amplified is converted into a current signal. CONSTITUTION:A voltage of a high frequency voltage signal source 100 is converted into a current signal by a resistor 11, fed to a transistor (Tr)20 of diode connection as the input stage of a current amplifier circuit 2 and the same forward bias voltage is given between the base and emitter of Trs 211-21n connected in parallel. The circuit 2 is of current mirror circuit constitution, currents IC21-IC2n the same as the input current Ii flow to the Trs 211-21n, a current being n-times of the current Ii flows to the emitter of the Tr31, converted into a voltage by a resistor 32 and extracted from a terminal 300 as a voltage output. The current amplification factor of the circuit 2 depends on the parallel number (n), which is stable independently of the operating current and temperature. The current amplification factor of the circuit 2 is nS21/S20 and given as (n) with S20=S21, where S20, S21 are emitter areas of Trs 20, 21 respectively.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a high frequency amplification circuit that amplifies a high frequency signal.
In particular, it relates to a high frequency amplifier circuit that operates stably in a high frequency band.

[Background of the invention]

As conventional wideband high frequency amplifier circuits, various local negative feedback voltage amplifier circuits using feedback impedance are used. In the case of a local return voltage amplification circuit using a feedback impedance, when a high impedance is used for the feedback impedance, the resistance is reduced due to the stray capacitance of the circuit, and when a low impedance is used for the feedback impedance, the transistor It has the disadvantage that it is easily influenced by the series impedance of active elements such as.

Therefore, in order to eliminate the drawbacks of the conventional high frequency amplification circuits described above, a current amplification method called a gain cell has been proposed as a wideband amplification circuit that obtains gain without using feedback impedance. However, this current amplification method requires a large number of stable current bias sources to obtain high gain, and requires a relatively high power supply due to multi-stage series operation, so it has the disadvantage that it cannot operate at low voltages. Ta.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high frequency amplifier circuit that eliminates the drawbacks of the conventional high frequency amplifier circuit and operates in a high band with stable gain.

[Summary of the invention]

The present invention provides that the current amplification operation of a transistor circuit operates faster than the voltage amplification operation.The present invention provides a diode connection in a current mirror circuit configured by pairing a transistor and a diode-connected transistor provided separately. Focusing on two points: the ratio of the current flowing through the circuit to the transistor current depends only on the size ratio of the emitter of each element, and after converting the voltage signal to be amplified into a current signal, each The device is characterized in that high frequency amplification is performed using a current circuit designed to match the dimensional ratio of the emitter of the element to a desired gain.

[Embodiments of the invention]

Preferred embodiments of the present invention will be described below with reference to the drawings, but first a current mirror circuit used in the present invention will be described.

FIG. 1 is a circuit diagram shown to explain the principle of a current mirror circuit. In this figure, transistor Ql
, Q2 are provided, and the base and collector of one transistor Q0 are commonly connected to form a diode connection, the base collector is connected to the input terminal T, and its emitter is grounded, and the base of the other transistor Q2 is connected to the input terminal T. is connected to the collector of the transistor Q1, the collector is connected to the power supply V through a resistance ratio, and the emitter is grounded. The current mirror circuit configured in this way has a current I equal to the input current I+. 2 is the load resistance R
can be passed to.

It is possible to flow current in this way, and the reason for this is as follows.

It is generally known that in silicon transistors, the collector-emitter saturation voltage (0.2V) is lower than the base-emitter voltage (Vpz=0.7V). Therefore, transistor Q1 does not saturate, and even though it is diode-connected in this way, I a l” h
The basic relationship holds: f e” In □. In the case of a transistor with a large hfe, I m 1 (
(If the relationship I - 1 holds true, the base current IBI can be ignored and I+ = L. Also,
A bias voltage vBΣ, which is sufficient to cause a collector current of Q2 to flow, is applied between the base and emitter of the transistor Q2, and this bias voltage is similarly applied between the base and emitter of the transistor Q2. Therefore, if the characteristics of the transistors QtQ2 are the same, ■. 1=I
a2 In other words, the relationship I i =I holds true.

The present invention aims to achieve stable amplification by establishing the above relationship.

FIG. 2 is a circuit diagram showing an embodiment of the high frequency amplifier circuit according to the present invention. In FIG. 2, 1 is a voltage-current conversion circuit that converts a high-frequency voltage signal into a high-frequency current signal, and this current-voltage conversion circuit consists of a voltage signal source 100 and a resistor (impedance 11). This current amplification circuit 2 is turned off by a current amplification circuit composed of a current mirror circuit. This current amplification circuit 2 consists of a transistor 20 whose base and collector are connected to form a diode connection, and n transistors whose collectors, bases, and emitters are each connected in common. transistor 2
11.21z t 213 +..., 2nd construction.

The base and emitter of the transistor 200 are connected to each transistor 211, 21□, 213 . .......

21 are connected in parallel between each base and emitter to form a current mirror circuit configuration. Each transistor 20 and 21. ．． 212, 213. .......

21' are transistors of the same type and have the same emitter area. Also, each transistor 20°211.
21z, 21g,..., 21. The current amplification factor of is assumed to be sufficiently large. Reference numeral 3 denotes a current-voltage conversion circuit, in which the collector of a transistor 31 whose base is forward biased by a voltage source 30 is connected to a high-voltage power supply terminal 35 via a resistor (impedance) 32.
0 connection, and the output terminal 300 is drawn out from the connection point.

The operation of the embodiment configured as above will be explained below.

First, the voltage of the high-frequency voltage signal source 100 of the voltage-current conversion circuit 1 is converted into a current signal by the resistor 11, and flows into the diode-connected transistor 20 of the input stage of the current amplifier circuit 20, and the transistors 211 to 211 connected in parallel. 21. Apply the same forward bias voltage between the base and emitter of the

Then, since the above circuit has a current mirror circuit configuration, n transistors 211 to 21 . , the same current as input current 1 is I@zl+I・22+I-2B+
”“°°Lae. 2. will flow. That is,
Engineering 1 = Iszi = Engineering sgz”'Lzs = ・・・・・・=
The relationship 1111 is established. Therefore, a current (n times i) that is n times the input current 11 flows through the emitter of the transistor 31 of the voltage-current conversion circuit 3, is converted into a voltage by the resistor 32, and is taken out as a stain voltage output from the output terminal 300. be done. That is, when the resistance value of the resistor 32 is set as a value, the output voltage Vo becomes Vo=nIiR.

According to such an embodiment, the current amplification factor of each transistor 20.21 of the current amplification circuit 2 is h f e.

When the number of parallel circuits is n, the total current m+1 amplification factor hfeo of the current amplifier circuit 2 is determined by n/(1+/hfe), and is stable without being affected by the magnitude of the operating current, temperature, etc. be. transistors 20 and 21
have the same emitter area as described above. Also,
Since the amplification factor hfeo of the circuit 2 is determined by the number of transistors 21, the emitter area of the transistor 20 is set to 8
2. If the emitter area of the transistor 21 is 821, hfeo=hfeo becomes hfeo=n. still,
nl! 31/82G is defined as the effective area.

In addition, the operating speed of the current amplification circuit 2 is such that the amplification section is in current amplification operation and the transistor 3 of the voltage-current conversion circuit 3 is
Since the base is grounded, extremely high-speed operation is possible.

In addition, if a high voltage transistor is used as the transistor 31, the output stage can be operated at a high voltage.

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

In the embodiment shown in FIG. 3, the difference from the first embodiment is that the circuit l for converting a voltage signal into a current signal is a P-channel MO.
B) The transistor is configured as a differential amplifier circuit, and the configuration will be explained below.

In other words, a differential stage for voltage-current conversion is constructed by a pair of MOB) transistors 12 and 13, and the bias current is set by a current mirror circuit consisting of MOB) transistors 15 and 16 and a resistor 19. has been done.

Also, the drain of one transistor 12 of the differentially connected MOB transistor is connected via two diode-connected transistors 17 and 18, and the drain of the other transistor 13 is connected to the input of the current amplifier circuit 2. connected to the end.

The current amplification circuit 2 includes transistors 20 . and 21□, 2
12 + 21a +..., 21. , but the transistors 20, 211 to 21 .
This embodiment differs from the first embodiment in that the base current of the input current 11 can be supplied separately from the input current 11. That is, the current amplification factor hfeo of circuit 2 in this connection is n (1'/I:1+hfe(hfe-1-1n/(n
+1):l), and the number of parallel connections n can be substantially increased. Thus, the output of the current amplification circuit 2 is connected to the source of the power transistor 32 of the voltage-current conversion circuit 3. The current-voltage conversion circuit 3 differs from the first embodiment in that the gate of the power MO transistor 32 is connected to the power supply end 250, and a constant forward bias voltage (for example, +5 V) is applied to the gate. It is in.

The operation of the second embodiment configured as above will be explained below.

When a signal voltage is applied between input terminals 110-120,
A constant current set in the MOS transistor 16 is shunted to the input of the current amplifier 2 in proportion to the polarity and magnitude of the signal voltage. The shunted input current 1 is amplified n times (nIi) by the current amplification circuit 2, converted to voltage by the current-voltage conversion circuit 3, and the amplified voltage output is taken out from the output terminal 300. Become.

According to the second embodiment shown in FIG. 3, high precision can be obtained in addition to the advantage that high frequency operation can be performed stably. That is, since the voltage-current conversion circuit 2 has a configuration of a differential amplifier circuit, it is not affected by the input common mode voltage or the diode drop voltage of the current amplification stage. Current amplifier circuit 2
Since the effect of the current increase rate of the transistor is small, in other words, the current amplification factor hfeo of the circuit 2 can be increased with high accuracy, and since the current voltage conversion circuit 3 is composed of MOS transistors, the bipolar transistor It has advantages such as not being affected by current amplification factors such as.

As described above, since the amplifier circuit according to the present invention is composed of circuits mainly consisting of active circuits, it is suitable for integration into an integrated circuit.

FIG. 4 shows a circuit block diagram within an integrated circuit suitable for applying the present invention to a color video monitor. Fourth
In the figure, a voltage-current conversion circuit IA-IC that converts a signal into a current is installed in a silicon (Si) substrate (chip) 500.
, current amplifying circuits 28 to 2C are provided for three channels corresponding to R, G, and B color signals, respectively.

This has the advantage that in addition to accurate gain and high-speed operation as a current amplifier, relative changes in each channel gain are small and hue reproducibility is good.

FIG. 5 is a circuit diagram showing still another embodiment of the present invention. The embodiment shown in FIG. 5 differs from the embodiment shown in FIG.
50, the current amplification circuit 2 and current-voltage conversion circuit 3 have the same structure as that shown in FIG. 2 described above.

When using the configuration shown in FIG. 5, the R, G, and B signals that are originally given as digital signals are converted to
50 converts it into an analog current signal and amplifies it in the current amplification circuit 2. This has the advantage that the analog amplification path is simple, the gain is excellent in stability, and the operating speed can be increased.

In each of the embodiments of the present invention, an example has been shown in which the output circuit can output a voltage with a high voltage amplitude, but if an amplified current signal output is required, the current-voltage conversion circuit 3 is of course unnecessary. Needless to say, if the current-voltage conversion circuit 3 is included, the operation will be faster.

As described above, according to each of the above embodiments, the amplification operation can be performed as a current amplification operation with little voltage change, so the operation speed becomes faster (the new station wave number f is 5G with a 5G transistor).
Assuming that the gain is 0 times, it is 500MHz/-3d). Further, since the actual amplification factor in each embodiment is determined only by the number of parallel transistors (effective area ratio), stability can be achieved with less influence of operating level, ambient temperature, etc.

Further, according to each of the embodiments described above, the circuit can be constructed mainly of active elements, so it is easy to integrate, and it is possible to reduce the size and cost.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a high frequency amplification circuit capable of stable operation and high band amplification.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram shown to explain the principle of a current mirror circuit, Fig. 2 is a circuit diagram showing a first embodiment of a high frequency circuit according to the present invention, and Fig. 3 is a circuit diagram showing another embodiment of the present invention. FIG. 4 is a block diagram showing a case where an embodiment of the present invention is applied to an integrated circuit, and FIG. 5 is a circuit diagram showing still another embodiment of the present invention. l... Voltage-current conversion circuit, 2... Current amplification circuit, 3
...Current voltage conversion circuit. Agent Patent Attorney Tatsunoge Unuma 1 Kasumi 20 3rd Sen

Claims (1)

[Claims] 1. In a high frequency amplification circuit that amplifies a high frequency signal, 1.
a voltage-current conversion circuit that converts the signal to be amplified into current;
A high frequency amplification circuit comprising a current amplification circuit that amplifies a current signal from the voltage-current conversion circuit by a current mirror circuit having a current amplification effect proportional to the effective area ratio of the transistor. z A high-frequency amplification circuit that amplifies a high-frequency signal includes a voltage-current conversion circuit that converts the signal to be amplified into a current, and a current amplification effect that is proportional to the effective area ratio of the transistor for the current signal from the voltage-current conversion circuit. A high-frequency amplification circuit comprising a current amplification circuit that amplifies a current signal using a current mirror circuit, and a current-voltage conversion circuit that converts a current signal into a voltage signal.