JPS59211305A - Bias circuit - Google Patents

Abstract

PURPOSE:To decrease the leakage component of an AC signal voltage by inserting an emitter follower circuit including a current mirror circuit between a DC power supply terminal and a DC bias input terminal of an amplifier as a DC bias circuit of the amplifier. CONSTITUTION:The current mirror circuit consisting of PNP transistors (TR) Q<3>, Q<5> and a bias supply circuit comprising the emitter follower consisting of an NPN TRQ<4> and a PNP TRQ<6> are provided between a DC bias input terminal (a) of voltage amplifiers 7, 9 and a common connecting point (b) of TRs Q<1>, Q<2>. Further, a voltage at a power supply terminal 2 is divided by resistors R<1>, R<2> and diodes Q<1>, Q<2> and a DC bias is given to an input terminal of the voltage amplifier through the emitter follower circuit comprising the TRs Q<4>, Q<6> and by connecting the input terminal 1 of the voltage amplifier 7 to a connecting point between the emitter of the TRQ<6> and the collector of the TRQ<5> via a resistor R<3>.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a DC bias circuit for a voltage amplifier, particularly a bias circuit suitable for integration into an integrated circuit. It is related to the 4th road.

(Conventional technology) FIG. 1 shows a conventionally well-known DC bias circuit.

To explain this, *'rh,'d'A Q+r: The ■ voltage of the child 2 is divided by the resistors R1 and R2, and the resistor R□, the 1μ between the connection point 4 of the 1st resistor and the input terminal 1 of the amplifier 70
] is connected to a resistor 4 (i:Ra) to provide an i-&+ current bias to the input terminal 1 of the amplifier 7. The same thing can be said about amplifier 9 as well. Is the AC input signal applied to the signal input terminal 6 connected to the DC blocking circuit C2? ;l! I is given the input terminal 1 vC of the voltage amplifier 7. Here, resistance R1 when applying an AC input signal
, R2 to the connection point 4 is given by the following equation (2), and is generally controlled by the capacitance 11j of the capacitor C+, and the chromatic tube to the other amplifier 9 can be ignored. set to the value.

Here, π is pi, f is input signal frequency, CI is value, Z4 is impedance when looking at the ground side from terminal 4, and VI is AC input signal voltage value. Assume that the impedance is so large as to be negligible.In reality, -ShioI], f=IKHz, CI=47μF, RI=R2
= 10 with Ω, Zn = 3.39Ω, 9, R3 = 50 with Ω
Then, it becomes 6.8X] 0' v+ in v4.

Incidentally, in integrated circuits, the increase in the number of external connection terminals and the increase in the number of external additional parts (single components that are connected to the external connection terminals of the integrated circuit and make up the entire circuit together with the integrated circuit) have affected their prices and shapes.

This is a big drawback. When the circuit in Fig. 1 is integrated, the area inside the broken line 5 is integrated, and
,10. and 11 are external connection terminals, and 9 and capacitors CI', C2, and C375 are externally added parts. In other words, there are seven external connection terminals and three external additional parts.

Next, as another conventional example, FIG. 2 will be shown in twilight.

In FIG. 2, parts corresponding to those in FIG. 1 are indicated by the same numbers, and the explanation thereof will be omitted. The point that stands out from Figures 1 and 1 is the resistor Ru connected in series between the power supply terminal 2 and the ground terminal 3.
, R2 is a collector-base connected transistor Q.
□lQ2 Kinteki 1] Return U1. Just the point, jljj1
The cropping conditions are the same as in the twilight shown in Figure 1 above.

In Figure 2, the r1 path has become a condensation, and the eve1tlj
The inner part of 5 is converted into a Toga circuit. 1st (n 1 and 4
)'y If this 1, 2° 3.4.8.10 and 11 are connected to the outside, capacitors CI, C2, and C3 are connected to the outside.

In other words, there are 7 external children, 81 outside;
τ] The number of processed parts is three.

(Object of the Invention) The object of the present invention is to reduce the fluctuation of the DC bias 91 and the terminal voltage of the 1% L pressure lees width meter when applying an AC input signal to the voltage amplifier, and to reduce the power to 4 = 4) The object of the present invention is to provide a complete bias circuit in which external connections and external additional parts are reduced in one circuit.

(Structure of the Invention) The circuit of the present invention includes a current mirror circuit in a bias circuit which has at least one voltage amplifier and supplies an rlV current and a bias to the input signal of the voltage amplifier I. The first guide that goes beyond the curve, the first type. &! 2 transistors, with their emitters connected to the collector output of said current mirror circuit - a third transistor with conductors 7 and 19, - their emitters connected to the collector outputs of said third transistors;

a fourth transistor of an opposite caster type, the collector of which is connected to the collector input of the current mirror circuit, the base of the fourth transistor being a DC bias input terminal;
The collector output of the current mirror circuit and the emitter of the third transistor are jointly i11', and the contact=point V+the output of the free current bias.

EXAMPLES Below, the present invention will be described in detail with reference to one drawing.

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

Note that parts corresponding to those in FIG. 1 and FIG. 2 are indicated by the same numbers, and the numbers are omitted.

In FIG. 3, the difference from the conventional relay shown in FIG. 2 is that PNP) transistors Qa, A current mirror circuit consisting of a transistor Q5 and an emitter follower of an NPN transistor Q4 and a PNI transistor Q6 are provided.

In Figure 3, "rM LE" of power supply terminal 2 is
+, R2 and diode QJ, Q2 are divided into 9 parts, and transistor Q4. The input terminal 1 of the voltage amplifier 70 is connected to the intersection of the emitter of the transistor Q6 and the collector of the transistor Q5 via the emitter follower circuit of the transistor Q6 via a resistor Ra.

A single current bias to the input terminal 1 of the voltage amplifier 7 is provided. The same holds true for the e+41 pressure amplifier 9.

The AC input signal applied to the signal input terminal 6 is applied to the input terminal 1 of the voltage amplifier 7 via the DC blocking capacitor C2. Here, when the AC input signal is applied, the collector of the transistor Q5, the emitter of the transistor Q6, the resistor Rs, the intersection with R4 ((the leakage of the AC input signal to the R1 point v, / is the following equation (4) is given by

・・・・・・(3) Here, ZQ5i'! ) Output impedance of transistor Q5, γ11Q6, emitter resistance of transistor Q6, hFEQ4. hFEQ6 is transistor Q
4. Q6's current amplification rate, z4/ is transistor Q
4 emitters hFEQ4, hFEQ6 is 100
γ before and after. , 6 are around several ohms, so the resistance value of R3 is set large so that the resistance value of 24' can be seen from the emitter resistance amplifier 9 of the transistor Q6. Positive 1 to resistor R4
Even if it is, it is -. In fact, - to give an example, Z
When Ω is set to 310°R3=50 in 4', v,/km, 25XIO'v, can be obtained, and the leakage v,/total can be easily made smaller than that of the conventional circuit.

Next, FIG. 4 shows a circuit diagram of another example: l/Iii 1+ll. In Figure 4, the point U that coincides with Figure J'-3,
PNP) transistor'tNPN transistor, N1)
By replacing the Nl transistor (i-PNP) transistor,
Circuit! 11 production situation +'i It is the same as shown in Fig. 3.

Here, the present invention has been integrated into one embodiment, as shown in FIG.

As shown in Fig. 4, the inside of the broken pig 5 is converted into a lunar phase (L11 path), and compared to the conventional example of the 21st prisoner in Fig.
1 V element, 1 external additional part IL'1j, f:l117
+・k 441 times 11? , can be provided.

(Effects of the Invention) As explained in detail above, according to the present invention, as the IC source 747 circuit of the amplifier, there is a Since the emitter follower circuit including the current mirror circuit is fully inserted, the leakage molecules of the AC signal voltage are extremely small, and the bias circuit #S is suitable for integrated circuits with few external connection terminals and external additional parts. can do.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams of a conventional example, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. 4 is a circuit diagram of an actual example of the present invention. In the figure, 1, 6, 11, 12...input terminals. 2...Electric terminal, 3...Grounding terminal, 4
...Bias terminal, ...Integrated circuit part, 7,9...Voltage amplifier, 8.10...
...Output terminal, R1-R5...Resistance. C□~C3... Capacitor, Ql, Q2. Q4
．． Q□. , Q□1゜Q1□...NPN) transistor + Q3 + Q61 Ql + Q7 rQ8.
Q,...PNP) transistor. I71ζ 1,000 1 Old Tanarei, Engineering 2] 1~6

Claims (1)

[Scope of Claims] It has at least one voltage amplifier and supplies one current bias voltage to the input terminal of the voltage amplifier. <In the IAS circuit, the first . Second
a third transistor of one conductivity type whose emitter is connected to the collector output of the current mirror circuit, and whose emitter is connected to the base of the third transistor and the collector output of the current mirror circuit. a fourth transistor of an opposite conductivity type connected to a collector input of the current mirror circuit. The base of the fourth transistor is connected to the input terminal of the input terminal (DC) of the fourth transistor, and the collector output terminal of the current mirror circuit is connected to the third transistor.
A bias circuit characterized in that a common connection point of the emitters of the transistors is used as a DC bias output terminal.