JPS6129573B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an amplifier, and particularly to an amplifier using bipolar transistors. Amplifiers are required to have low distortion characteristics, and for this purpose, a method of suppressing distortion by applying negative feedback is widely used. However, a decrease in amplification due to negative feedback is unavoidable, and thus not only are many amplification elements required to obtain the desired amplification, but there is also the risk that the stability of the entire amplifier circuit will deteriorate and oscillation may occur. exist. Especially in transistors, which are amplification elements,
Since its input/output characteristics exhibit nonlinearity, large currents are passed or negative feedback is applied to improve this nonlinearity, but neither of these methods are desirable, especially the solution using negative feedback. It still has the above-mentioned drawbacks. An object of the present invention is to provide an amplifier circuit with a simple configuration that can improve the nonlinear distortion of an amplifier transistor without applying negative feedback. The amplifier circuit of the present invention compensates by canceling out the base-emitter voltage of an amplifying transistor to which an input signal is applied to the base with the forward voltage of a separately provided PN junction element such as a diode. The feature is that between an impedance element whose one end is connected to the emitter of the amplification transistor and the other end of this impedance element and a reference potential point, it exhibits a high impedance in the direction of the current flowing through the transistor. The device includes a PN junction element connected in a manner such that It's because I did it. The present invention will be explained below with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention, in which an emitter resistor R _E is connected to the emitter of an NPN transistor Q ₁ to which an input signal V _IN is applied to the base, and this resistor R _E and a reference A diode _D1 is provided between the ground point and the potential. As shown in the figure, this diode _D1 exhibits a high impedance in the direction of the current ₁ flowing through the transistor _Q1 , and is connected with a polarity that prevents the current ₁ from flowing into the transistor Q1. For example, current mirror circuits ₁ and 2 provide a constant ratio of currents ₁ and ₄ (I ₁ / ₄ = 1/α, α is constant) to these transistors Q 1 and diode D ₁ .
is provided. Current mirror circuit 1 is a PNP transistor whose bases are commonly connected to each other.
It consists of Q ₂ , Q ₃ and Q ₄ and emitter resistors R ₁ , R ₂ and R ₃ , and the transistor Q ₂ has a diode configuration with its base and collector commonly connected.
Each transistor _Q2 to _Q3 depends on the selection of resistors _R1 to _R3 .
The ratio of the output currents ₁ , ₂ and ₃ of can be selected as desired. The output current of the transistor Q ₂ is the supply current ₁ of the transistor Q ₁ , and the output current ₃ of the transistor Q ₄ is the supply source of the output load resistance R _L. The current mirror circuit 2 consists of NPN transistors Q ₅ , Q ₆ and Q ₇ whose bases are commonly connected to each other and emitter resistors R ₄ , R ₅ and R _6. The transistor Q ₇ has a diode configuration and the resistor R ₄ ～ _R6
By selecting , the output current of each transistor Q ₅ to Q ₇ is selected as desired. In this example, the collector outputs of the transistors Q ₅ and Q ₆ are commonly connected to each other and connected to the common connection point of the diode D ₁ and the emitter resistor _RE , and the sum of currents ₁ and ₄ is current ₅ = _1. It is configured to suck in ₊₄ . The collector output of the transistor Q ₇ and the collector output of the transistor Q ₃ of the mirror circuit 1 are commonly connected, so that the current values of both the mirror circuits 1 and 2 are associated with each other. For example, by selecting all the resistors R ₁ to R ₆ to have equal values, ₁ =
The current values are determined so that ₂ = ₃ (α = 1) and ' ₅ = 2 ₄ . In such a configuration, diode D ₁ and resistor R _E
By setting the potential at the connection point to Va, the forward voltage of the diode D ₁ to V _BE2 , and the base-emitter voltage of the transistor Q ₁ to V _BE1 , the following equation is established. ₁ = (V _IN −V _BE1 −Va)/R _E ...(1) Since Va=−V _BE2 here, equation (1) becomes the following equation. ₁ = (V _IN -V _BE1 +V _BE2 )/R _E (2) Therefore, the output V _OUT is expressed by the following formula. V _OUT = ₃ R _L = ₁ R _L = R _L /R _E {V _IN −(V _BE1 − V _BE2 )}……(3
) Here, the relationship between the voltage V _BE of the PN junction of a transistor or diode and the current is generally expressed by the following equation. V _BE ≒kT/qln/ _S ...(4) where k is Boltzmann constant, T is junction temperature,
q is the electronic charge, and _S is the reverse saturation current. Therefore, transistor Q ₁ and diode D ₁
Let the junction temperatures of T ₁ and T _{2 be T 1 and T 2} , and the saturation current _S
1 and _S2 , the following equations hold true.

[Table] 〓……………………(5)
kT ₂

Claims (1)

[Claims] 1 A first transistor to which an input signal is applied to the base, an impedance element having one end connected to the emitter of the first transistor, the other end of the impedance element having the same conductivity type as the first transistor, and a reference potential. a second transistor whose emitter and base are respectively connected to a point and whose collector is supplied with power through an element equivalent to the impedance element; and a first current flowing between the collector and emitter of the first transistor at a constant ratio. a first current mirror circuit that generates second and third currents having a relationship of a second current mirror circuit that converts the sum of fourth currents flowing between the collector and emitter of the second transistor into a current having a fixed ratio relationship with the second current, and outputs an output in response to a change in the third current. An amplifier designed to derive