JP2706146B2 - Semiconductor integrated circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor integrated circuit.

[Conventional technology]

 FIG. 2 is a circuit diagram of a conventional reference constant current source circuit.

The output current of the reference constant current source is the sum of the collector current and the collector current of the transistor Q ₂ of the transistor Q _1.

The collector current of the transistor Q ₁ is, since the base of the transistor Q ₁ is constitutes a transistor and a current mirror circuit in the temperature dependence no constant current source 1, there is no dependence of the temperature. That is, the temperature coefficient of the current value is zero.

The collector current of the transistor Q ₂ is, since substantially equal to a value obtained by dividing the voltage between the base and the emitter of the transistor Q ₃ by the resistor R _2, with the temperature dependence is equal to the base-emitter voltage of the transistor. That is, the temperature coefficient of the current value is about −3000 ppm / ° C. at room temperature.

From the above, in this circuit, by appropriately selecting the values of the resistors R ₁ and R ₂ and setting the ratio between the collector current of the transistor Q _{1 and} the collector current of the transistor Q ₂ to an appropriate value,
An output current having an arbitrary temperature coefficient in the range of 0 to -3000 ppm / ° C can be obtained.

 FIG. 3 is a circuit diagram of a conventional voltage controlled oscillation circuit.

This circuit is constituted by the amplifier stage consisting of transistors Q ₄ and Q _5, the amplifier stage is cross bonded through a buffer amplifier comprising transistors Q ₈ and a current source 7 and the transistor Q ₉ and the current source 8. The voltage amplifier stage of the inter-terminal voltage is determined by the base-emitter voltage of the terminal potential and the transistor Q ₆ and Q ₇ of the resistor R _5, the load comprising a transistor Q ₁₀ which is clamped a resistor R ₃ and R ₄ Have. The emitter of the transistor Q ₄ and Q ₅ is biased by the constant current source 5 and 6 are coupled through a timing capacitor C.

The oscillation frequency f of the voltage controlled oscillator circuit includes paired constant current source 5 and 6, a constant current source 7 8, the transistor Q ₄ and Q _5,
Transistor Q ₆ and Q _7, the transistor Q ₈ and Q _9, and a resistor R ₃
If all the characteristics of R and R ₄ are equal, Equation (1) is obtained. Here, I ₁ is the current value of the constant current source 5 and 6, C is the capacitance of the capacitor C, the V _BE is the base-emitter voltage of the transistor Q ₆ and Q _7.

By the transistor Q ₁₀ and the resistor R ₃ and R ₄ to vary the emitter current flowing through the transistor Q ₆ and Q ₇ become accompanied by temperature changes, before (1) the base-emitter voltage of the transistor Q ₆ and Q ₇ It is provided to compensate for the temperature of V _BE and improve the temperature characteristics of frequency f.

[Problems to be solved by the invention]

In conventional semiconductor integrated circuits, the reference constant current source is provided with temperature characteristics to compensate for the temperature characteristics of a specific circuit. In some cases, the optimum compensation condition changes depending on the condition.

A voltage controlled oscillator circuit is a typical example, and it is very difficult to design a temperature characteristic to a target value, especially at a high frequency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and facilitates the design of temperature characteristics, and provides a semiconductor device that can obtain optimum temperature characteristics according to operating conditions even after being integrated. It is intended to obtain an integrated circuit.

[Means for solving the problem]

In the semiconductor integrated circuit according to the present invention, the output current is obtained by adding an appropriate ratio of the outputs of the two constant current sources having different temperature coefficients, and a ratio of the output of the two constant current sources is added. Are provided with a plurality of combinations different from each other, and an arbitrary combination can be selected from the plurality of combinations by an external logic symbol.

Further, a voltage-controlled oscillation circuit according to the present invention is characterized in that the semiconductor integrated circuit is used as a reference current source.

[Action]

In the semiconductor integrated circuit according to the present invention, a combination of two types of constant current sources having different temperature characteristics can be arbitrarily selected, so that the temperature characteristics can be easily designed,
Even after being integrated, an optimal temperature characteristic can be obtained according to the operating conditions.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a semiconductor integrated circuit showing one embodiment of the present invention.

In _{FIG, S 11 ~S 1n S 21 ~S} 2n is an analog switch, the only ON analog switch connected to the terminal which is the "H" level in the output terminal of the decoder 3. The analog switch which is turned ON and S ₁₁ ~S _1n S ₂₁
1 to _2n , the equivalent circuit viewed from the output terminal 2 is the same as that of FIG. For example, if the analog switches S ₁₂ and S ₂₂ is ON, the first
The transistors Q ₁₂ and Q ₂₂ , the resistors ₁₂ and R ₂₂ shown in FIG.
It corresponds to the conventional transistors Q ₁ and Q ₂ and the resistors R ₁ and R ₂ in FIG.

The temperature coefficient of the current value output to the output terminal 2 is the resistance R ₁
And it is determined by the value of R _2. Resistors R ₁₁ and R ₂₁ , R ₁₂ and R ₂₂ ,
... If all combinations of R _1n and R _2n are selected and set to different values so as to obtain different temperature coefficients, an arbitrary combination of resistances can be selected by a logic signal externally applied to the terminal 4, and as a result, Thus, an output current having an arbitrary temperature coefficient can be obtained.

Also, in the conventional voltage-controlled oscillation circuit shown in FIG. 3, if the reference constant current source shown in FIG. 1 is used as the reference constant current source _Iref for temperature compensation, any temperature compensation condition can be given by an external logic signal. Can be.

〔The invention's effect〕

As described above, according to the present invention, an arbitrary combination can be selected by an external logic signal from a combination of constant current sources having different temperature coefficients prepared for a plurality of output currents. In the case where the compensation conditions are different depending on the operating conditions, there is an effect that the optimum temperature compensation conditions can be easily realized even after being integrated.

Also, in a voltage controlled oscillator circuit using this semiconductor integrated circuit as a reference constant current source, the temperature characteristics of the oscillation frequency can be easily set as desired, and even when the compensation conditions differ depending on the oscillation frequency, the optimum characteristics can be optimally programmed by an external signal. There is an effect that compensation can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a semiconductor integrated circuit showing one embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional reference constant current source circuit, and FIG.
FIG. 1 shows a circuit diagram of a conventional voltage controlled oscillation circuit. Q _{1 to} Q ₁₀ , Q _{11 to} Q _1n , Q _{21 to} Q _2n ...... Transistors, R _{1 to} R ₅ ,
R _{11 to} R _1n , R _{21 to} R _2n ...... Resistance, S _{11 to} S _1n , S _{21 to} S _2n … Analog switch, Vcc… Power supply voltage, V _B … Bias power supply, I _ref … Temperature compensation Reference constant current source, Vc ... Control voltage input terminal, C ... Timing capacitor, 1 ... Constant current source without temperature dependency, 2 ... Output terminal, 3 ... Decoder, 4 ... External logic signal input Terminals, 5-8: current source. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] An output current is obtained by adding an appropriate ratio of outputs of two types of constant current sources having different temperature coefficients, and a combination having a different ratio of addition of outputs of the two types of constant current sources is used. A semiconductor integrated circuit comprising a plurality of units, wherein only one of the plurality of combinations can be selected by the external logic signal.