JPH0322083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transistor amplifier.

[Prior Art] A transistor amplifier includes a current feedback type emitter amplifier circuit in which a resistor is connected to the emitter of a transistor.
As shown in the figure. The emitter of transistor _Q1 is connected to the negative power supply -B through the emitter resistor R _E , and the collector is connected to the positive power supply + through the collector load resistor R _C.
Connected to B. The configuration is such that an input signal V _i is applied to the base and is derived from the collector as an output V ₀ .

Transistor which is an amplification element of circuit 1 in Fig. 1
If h _FE of Q ₁ is large enough, the collector power supply I _C
is almost equal to the emitter current I, and if this is _I0 , then _I0 =(Vi-VBE1)/RE...(1) holds true. Here, V _BE1 is the base-emitter voltage of transistor Q1. Also, the output voltage
V ₀ is expressed by the following formula.

V ₀ =+B−I ₀ R _C ...(2) The following equation is obtained from equations (1) and (2).

V ₀ = (+B-R _C /R _E・Vi)+R _C /R _E・V _BE1 ...(3) [Problem to be solved by the invention] As is clear from equation (3), the amplification shown in FIG. It can be seen that in the output voltage of the circuit, in addition to the original output (+B-R _C /R _E ·Vi), a so-called distortion component called R _C /R _E ·V _BE1 is generated. This is due to the nonlinearity of the transistor, and since the base-emitter voltage V _BE has a nonlinear relationship with I ₀ , such an amplifier inherently has distortion.

There is a method of providing negative feedback to eliminate such distortion, but applying negative feedback leads to a decrease in the amplification degree, and it is necessary to use a large number of amplification elements to obtain the required amplification degree.

[Means for Solving the Problems] An object of the present invention is to provide a transistor amplifier capable of removing distortion components caused by nonlinearity of an amplifying element with a simple circuit configuration.

The means of the present invention for achieving the above object comprises a first transistor to which an input voltage is applied to the base, and the ratio of the output voltage derived to the collector of the first transistor to the input voltage is:
a first amplifier circuit of n (n is an integer of 2 or more);
a second transistor of a common emitter type having a base to which the output voltage derived to the collector of the first transistor is applied through (n-1) Darlington-connected transistors; The first transistor, the Darlington-connected transistor, and the second transistor have the same conductivity type.

[Example] The present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram showing the basic operating principle of the present invention. The amplifier circuit 1 has the same configuration as the circuit shown in FIG. 1, and an inverting amplifier circuit 2 is used in the preceding stage of the amplifier circuit 1. Amplifier circuit 2 is transistor Q ₂
and this transistor Q ₂ has a transistor Q ₁
It is an NPN transistor of the same conductivity type as the resistor
The collector is connected to the positive power supply + _{B through the load resistor R A ,} and the circuit input V _i
is applied to the base, which is the control electrode of transistor Q ₂ , and the output V _A from the collector as the output voltage
is derived and the control electrode input of transistor Q ₁ ,
In other words, it is the base input. Note that the positive power supply of the amplifier circuit 1 is + _B2 .

In such a circuit configuration, the output V _A of the front-stage amplifier circuit 2 and the output V ₀ of the rear-stage amplifier circuit 1 are respectively expressed by the following equations.

V _A = +B ₁ −R _A /R _B (V _i −V _BE2 ) …(4) V _O = +B2−R _C /R _E (VA−VBE1) …(5) (4), (5) The following equation is obtained from the equation.

V _O = +B ₂ −R _C /R _E {+B ₁ −R _A /R _B V _i + (R _A /R _B V _BE2 −V _BE1 )} ...(5), and the distortion term in equation (6) becomes (R _A / R _B V _BE2 − V _BE1 ). Here, if transistors Q ₁ and Q ₂ have the same characteristics, for example, if they are formed on the same semiconductor chip, then the current I _A
When and _IO are equal, the base-emitter voltages V _BE1 and V _BE2 of both transistors are equal, and therefore the above distortion term becomes (R _A /R _B -1) V _BE . Therefore, by selecting R _A = R _B , the distortion term becomes zero, and no distortion occurs in the output V _O. In addition,
Since it is necessary to equalize the amount of feedback by the resistors R _B and R _E , it is also necessary to set R _B = R _E.

Setting the resistances R _A and R _B of the preamplifier circuit 2 to be equal in this way means making the amplifying circuit 2 an amplifying circuit with a voltage gain of 1, thereby making it possible to remove distortion components.

FIG. 3 is a circuit diagram showing an embodiment based on the basic operating principle of the present invention, in which transistors _Q1 and
This shows the case where Q ₂ is an N-channel junction field effect transistor. The circuit input V _i is applied to the gate, which is the control electrode of the transistor Q ₂ ,
A drain is used as the output electrode, and the output V _A is led from the drain. The output is applied to the gate, which is the control electrode, of the transistor _Q1 , and the circuit output V _O is derived from the drain, which is the output electrode. By making the gate-source voltage V _GS of both transistors equal and making the resistors R _A and R _B also equal, the distortion component can be similarly removed from the output V _O.

In the circuits shown in Figures 2 and 3 above, R _A =
As R _B , the ratio of the output voltage to the input voltage of the preamplifier circuit 2 is 1, that is, the voltage gain is 1. However, in the amplifier according to the present invention shown below, the voltage gain of the preamplifier is 2 or more. In the circuit of the embodiment shown in FIG. 4, the voltage gain of the preamplifier 2 is set to 2.

In other words, with R _A /R _B = 2, Darlington connection is made to transistor Q ₁ of amplifier circuit 1 in the subsequent stage.
Provide an NPN transistor Q ₃ , and this transistor
The collector output of transistor Q ₂ at the base of Q ₃ V _A
This is a configuration that applies . Therefore, the output V _A is the two-stage base-emitter of transistors Q ₃ and Q ₁ .
In order to pass through the PN junction, the distortion term shown in equation (6) is shown as the following equation.

(R _A /R _B・V _BE2 −V _BE3 −V _BE1 ) ...(7) Here, if R _A /R _B = 2 and all transistors have the same characteristics, then V _BE1 = V _BE2 = V _BE3 , and therefore, term (7) can be set to zero.

Generally, the voltage gain of the preamplifier circuit 2 is set to n (n is 2
(integer above) and R _A /R _B = n, then (n-1) stage Darlington connection transistor Q ₃ is connected to transistor Q ₁ of the rear stage amplifier circuit 1,
Distortion can be removed by making the conductivity types of each of the transistors Q ₁ to Q ₃ the same.

That is, an (n-1) stage Darlington connection transistor _Q3 is provided between the output V _A and the base of the transistor _Q1 , and the transistor _Q1 and the (n-
1) If the Darlington connection transistor _Q3 is further connected to the Darlington transistor, the output
V _A is input to the base of transistor Q ₁ through (n-1) PN junctions to achieve a predetermined purpose.

[Effects] As detailed above, according to the present invention, distortion caused by nonlinearity of the amplifying element can be removed with a simple circuit configuration without applying negative feedback, so that a good transistor amplifier can be obtained. can get.

Moreover, since the first transistor, the Darlington connection transistor, and the second transistor are of the same conductivity type, it is easy to make the base-emitter voltages of each transistor the same, and the distortion can be reliably removed. be able to.

Furthermore, a voltage gain can be obtained by the first and second amplifier circuits, and a current gain can also be obtained by the Darlington-connected transistors.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional transistor amplifier, FIGS. 2 and 3 are circuit diagrams showing the basic operating principle of the present invention, and FIG. 4 is a circuit diagram showing an embodiment of the present invention. . Explanation of symbols of main parts, 1...
Post-stage amplifier circuit, 2...Pre-stage amplifier circuit, Q ₁ , Q ₂ ...
…Transistor, Q ₃ …Darlington connection transistor.

Claims (1)

[Scope of Claims] 1 A first transistor to which an input voltage is applied to the base, the ratio of the output voltage derived to the collector of the first transistor to the input voltage is n (n is 2 an integer greater than or equal to); and a grounded emitter having a base to which the output voltage derived to the collector of the first transistor is applied via (n-1) Darlington-connected transistors. a second amplifier circuit comprising a second transistor of the same type as the first transistor, and the conductivity type of the first transistor, the Darlington-connected transistor, and the second transistor are the same as each other. transistor amplifier.