JPH03272209A - Amplifier - Google Patents

Abstract

PURPOSE:To form an amplifier circuit at high speed and low power consumption with only an NPN transistor(TR) by providing the NPN drive TR, a constant current circuit connecting to its collector and a current mirror circuit comprising 1st and 2nd TRs. CONSTITUTION:An NPN TR is employed for a drive TR 1, its collector connects to a positive voltage terminal (+) through a constant current circuit 4 and its emitter connects to a negative voltage terminal (-) through a current mirror circuit 2. The current mirror circuit 2 consists of a 1st TR 2A connecting in series with the drive TR 1 and a 2nd TR 2B whose base and collector are connected in common to a base of the 1st TR 2A and whose common connecting point of the base and collector connects to a common connecting point between the constant current circuit 4 and th drive TR 1 through a voltage shifter.

Description

Detailed Description of the Invention "Industrial Application Field J This invention can be used, for example, as an amplifier to provide a drive signal to an IC under test in an IC test device, or to transmit X and Y drive signals from an oscilloscope to a cathode ray tube. The present invention relates to an amplifier that can be used as a power amplifier.

``Conventional technology J In IC test equipment, a drive circuit that supplies a test pattern signal to an IC under test is configured to apply current to the IC under test in accordance with the logical value (H or L) of the test pattern signal supplied to the IC under test. A function is required to perform both the operation of injecting current and the operation of drawing current from the IC under test.

For this reason, an emitter follower circuit shown in FIG. 7 has conventionally been used as a drive circuit.

``Problem to be solved by the invention'' In a built ivy follower circuit, load 3 has a distance of ±50m, for example.
When trying to supply a current of A, connect a 50mA constant current circuit 2 to the emitter side of the transistor 1 constituting the industrial vine follower, and draw a 50mA current from the load 2 while the transistor 1 is off (- 50mA)
It is configured so that it can be done.

That is, in this case, when a current of +50 mA is flowing into the load 3, a current of 100 mA flows through the transistor 1, and when the current flowing through the load 3 is O, 50 mA flows through the transistor 1. Therefore, it has the disadvantage of high power consumption.

In an IC test device, the drive circuit requires a minimum number of terminals of the IC under test. For this reason, I
Since an IC testing device for testing C requires at least as many drive circuits as the number of terminals, the number of drive circuits is large.

Therefore, the capacity of the power supply that supplies power to this drive circuit also needs to be large.

For this reason, it is conceivable to use a complementary amplifier circuit configured by connecting an NPN transistor and a PNP transistor in series, for example, but the PNP transistor used in the complementary amplifier circuit has a lower operating speed than an NPN transistor. Inferior in pressure resistance.

This tendency becomes even more pronounced when the circuit is integrated into an IC.

The purpose of this invention is to achieve high speed using only NPN transistors.
The aim is to construct an amplifier with low power consumption.

"Means for Solving the Problem" In the first invention of this application, the N
a PN type drive transistor, a constant current circuit connected to the collector side of this drive transistor, a first transistor connected in series with this drive transistor, and a base and a collector commonly connected to the base of this first transistor, An amplifier circuit is constructed by: a current mirror circuit constituted by a second transistor whose common connection point between the base and the collector is connected to the common connection point between the constant current circuit and the drive transistor through a voltage shifter;

According to the configuration of the first invention, the current flowing through the drive transistor is detected by the second transistor constituting the current mirror circuit, and a voltage signal inversely proportional to the current flowing through the drive transistor is sent to the first transistor via the second transistor. give.

As a result, when the current flowing through the drive transistor attempts to increase, a voltage signal in the reverse bias direction is applied to the base of the first transistor constituting the current mirror circuit.

Therefore, the impedance of the first transistor increases,
The current flowing through the first transistor is throttled. Therefore, most of the current flowing through the drive transistor is discharged to the load side. In other words, the current applied from the power source is effectively transmitted to the load.

On the other hand, when the current flowing through the drive transistor is about to decrease, the first transistor constituting the current mirror circuit detects the decrease in the current flowing through the drive transistor, and the base of the second transistor constituting the current mirror circuit detects the decrease in the current flowing through the drive transistor. Provides a voltage signal in the forward bias direction.

As a result, the impedance of the first transistor is controlled to decrease, increasing the amount of current drawn from the load side.

As described above, according to the invention No. 2 of this application, the first transistor connected in series with the drive transistor operates in an apparent complementary manner to the operation of the drive transistor, and effectively utilizes the electric power given from the power supply. An amplifier with low power consumption can be provided. Furthermore, since it can be constructed using NPN transistors, it is possible to provide an amplifier that can withstand high-speed operation and large-amplitude output.

In the second invention of this application, a plurality of first transistors constituting a current mirror circuit are connected in parallel so that the amount of change in the current flowing through the first transistors can be increased.

By increasing the amount of change in the current flowing through the first transistor, the amount of current that changes complementary to the change in the current flowing through the drive transistor increases, making it possible to obtain a large amount of change in the current output to the load. can. Therefore, it is possible to provide an amplifier that can output large amplitude power to a load without increasing power consumption.

A second invention of this application proposes an amplifier in which a plurality of first transistors constituting a current circuit are connected in parallel.

According to the configuration of the second aspect of the invention, it is possible to reduce the value of current flowing through the drive transistor when there is no signal. As a result, an amplifier with low power consumption can be provided.

In the third invention of this application, a switch element is provided on the input side of the drive transistor, and by controlling this switch element to turn on as necessary, the drive transistor and the first transistor constituting the current mirror circuit are turned off. It is configured so that it can be done.

According to the third aspect of the invention, the drive transistor can be controlled to be turned off as required, so that the output impedance can be controlled to a high impedance state.

By being able to control the output impedance to a high impedance state, the signal output from the load can be effectively taken out to the signal acquisition circuit that takes in the signal from the load.

In other words, when the load is an IC, the IC shares one terminal as an input terminal and an output terminal. For this reason, each terminal of the IC under test is connected to a driving amplifier that provides a test pattern signal and a signal acquisition circuit that takes in the signal. Therefore, when a signal is captured by the signal capture circuit, by controlling the driving amplifier to a high impedance state, the response output signal output from the IC can be effectively captured by the signal capture circuit.

A fourth invention of this application proposes a configuration in which a potential absorption transistor is connected in series between the emitter of the drive transistor and the collector of the first transistor constituting the current mirror circuit.

According to the configuration of the fourth invention, the collector potential of the first transistor constituting the cant mirror circuit is maintained at a constant potential by the operation of the potential absorption transistor.

As a result, charging current and discharging current do not flow to the capacitance formed between the collector base of the first transistor, so that the operation of the first transistor can be made faster.

A fifth invention of this application proposes a configuration in which a constant voltage element is connected between the collector and base of the second transistor constituting the current mirror circuit to maintain the collector-base potential at a constant value.

According to the configuration of the fifth invention, the voltage between the collector and base of the second transistor constituting the current mirror circuit is maintained at the constant voltage of the constant voltage element by the connection of the constant voltage element. Charging and discharging operations for capacitance can be eliminated.

As a result, there is an advantage that the operation of the second transistor can be made faster.

"Example" FIG. 1 shows an embodiment of the first invention of this application.

In FIG. 1, 1 is a drive transistor, 2 is a current mirror circuit, and 3 is a load.

As the drive transistor, an NPN type transistor is used.
Its collector is connected to the positive voltage terminal (2) through the constant current circuit 4, and its emitter is connected to the negative voltage terminal O through the current cooler circuit 2.

The current mirror circuit 2 includes a first transistor 2A connected in series with the drive transistor 1, and detects an increase or decrease in the current 11 flowing through the drive transistor 1, and connects the first transistor 2A to the base of the first transistor 2A. The second transistor 2B provides a control signal to perform an operation in the opposite direction, and the voltage shifter 2C connects the collector of the second transistor to the connection point between the drive transistor 1 and the constant current source 4.

Both the first transistor 2A and the second transistor 2B are constituted by NPN transistors, the terminals of which are connected to the negative voltage terminal e, the bases of both are commonly connected, and the collector and base of the second transistor are commonly connected, The common connection point is connected to the connection point between the drive transistor 1 and the constant current element through the voltage shifter 2C.

The voltage shifter 2C can be configured by, for example, a Zener diode. The voltage shift amount (2) of the voltage shifter 2C is selected to be a voltage that applies a constant positive voltage between the collector and emitter of the drive transistor 1 and does not saturate the drive transistor 1.

In the circuit configuration shown in FIG.
11 is the current flowing through the current mirror circuit 2, I2 is the current flowing through the first transistor 2A constituting the current mirror circuit 2, and G is the current flowing through the first transistor 2A constituting the current mirror circuit 2.
The current flowing through the second transistor 2B constituting the error circuit 2 is I3, the current flowing through the constant current circuit 4 is Iref, and the current output to the load 3 is I. ut, then 1 + + I 3= I rGr (constant) 111z=
I-, t13=12.

In other words, I when there is no output. When ut-O, the current ■ flowing through the drive transistor 1 and the current I2 flowing through the first transistor 2A are I,=1. The values are equal. Further, in this state, the current I3 flowing through the second transistor 2B constituting the current mirror circuit 2 is in a state of 12=T3.

1 In this state, when a positive voltage is applied to the base of the drive transistor 1 and the current 2 flowing through the drive transistor 1 increases, the output current I increases by the increased amount Δh. t begins to flow. At the same time, since Il+I3 is constant, current I3 decreases by the increased amount.

When the current I3 decreases, the base current flowing into the base of the first transistor 2A constituting the current mirror circuit 2 decreases, and thereby the collector-emitter resistance value of the first transistor 2A is controlled to increase.
The current I2 flowing through the transistor 2A is controlled to decrease.

As a result, the current Δ■2 corresponding to the decrease in the current I2 flowing through the first transistor 2A becomes the output current I. Output as ut. In other words, the output current ■. , is the increase in current ■1 Δ11
and the sum of the decrease ΔI2 in the current I2 (ΔL+Δ12).

On the other hand, the output current I. □ is I. , t=0, when a negative voltage is applied to the base of the drive transistor 1, the current 12 flowing through the drive transistor 1 decreases. At this time, the first transistor 2A constituting the current circuit 2 tries to keep the current I2 flowing, so the current II given from the drive transistor 1
The decrease -Δ11 is absorbed from the load 3.

At the same time, as the current 1 flowing through the drive transistor 1 decreases, the current I3 increases and the base current of the first transistor 2A increases.

Therefore, the collector-emitter resistance value of the first transistor 2A decreases, and the current 2 is controlled in the direction of increasing. As a result, the current flowing through the first transistor 2A increases in proportion to the increase in current 3, and the increased current is drawn from the load 3.

As described above, according to the first invention of this application, although configured with NPN transistors, the drive transistor 1 and the first transistor operate complementary to each other, and output a current change with a large amplitude to the load 3. I can do it.

FIG. 2 shows an embodiment of the second invention of this application.

In the second invention, a plurality of first transistors 2A constituting the current error circuit 2 are connected in parallel, and the second transistor 2A is connected in parallel.
The structure is such that the change in the current I3 flowing through B can be multiplied by a parallel number and extracted, thereby allowing the output current to be efficiently extracted to the load 3.

For this reason, in addition to the current mirror circuit 2, a current mirror circuit 5 is provided on the collector side of the drive transistor 1.
The current 11 flowing through the drive transistor 1 is multiplied by a parallel number and changed by this current error circuit 5 and the current error circuit 2.

That is, the collector of the transistor 5A constituting the current mirror circuit 5 is connected to the positive voltage terminal (2), and the collector of the transistor 5B is connected to the positive voltage terminal (2) through the constant current diagram FIIr4. The bases of the transistors 5A and 5B are commonly connected, and an appropriate potential 1 located on the positive side of the potential of the collector of the drive transistor 1 is applied to the commonly connected bases. The terminals of transistors 5A and 5B are commonly connected to the collector of drive transistor 1.

With this configuration, the current mirror circuit 5
A current r having a ratio of 1:1 flows through the transistors 5A and 5B constituting the drive transistor 1, and a current r of 21. current flows.

Therefore, the first transistor 2A constituting the current mirror circuit 2 provided on the emitter side of the drive transistor l is 2
The transistors are connected in parallel, and a current 2I2 having a ratio twice the current I2 flowing through the second transistor is drawn from the drive transistor 1.

According to this circuit configuration, there is a relationship of 1+-L-r Iz Iot-21+ 2 I2. This gives an output current I. It can be seen that the current I2 changes depending on U.

As a result, in a circuit that has the maximum supply capacity of Iout-±50 mA, the current that must be allowed to flow during no load can be reduced to 37.5 mA. Incidentally, according to the circuit configuration shown in FIG. 1, the current that must be allowed to flow during no load is 50 mA.

Therefore, according to the second invention, it is possible to construct an amplifier capable of complementary operation using only NPN transistors, and to reduce its power consumption.

In the embodiment shown in FIG. 2, the case where the current ratio of the current mirror circuit 2 is set to 2=1 has been explained, but in FIG.
Two or more can be connected in parallel. The example in FIG. 3 shows a case where five first transistors 2A are connected in parallel and the current ratio is 5:l.

In this case, if I ref = 10 mA, ±50
A driving capacity of mA is obtained. At this time, the maximum current flowing through the circuit is 60 mA (when 50-min is drawn), and the current flowing during no load is 30 mA.

FIG. 4 shows an embodiment of the third invention of this application.

In the third invention of this application, a switch element 6 is provided at the 6 input terminal of the drive transistor 1, and by controlling this switch element to turn on, the drive transistor 1 is controlled to be in an OFF state, and when viewed from the load 3 side, the switch element 6 is turned on. - It provides an amplifier configured to be able to adopt impedance states.

In this example, the switch element 6 is configured by a circuit configuration in which transistors 6A and 6B are differentially coupled. A current I flowing through the second transistor 2B forming the current mirror circuit 2 by controlling the transistor 6A forming the differential circuit to turn on and turning 6B to turn off passes through the diode 2D and the base of the first transistor 2A, and further It is drawn into transistor 6A through diode 7.

As a result, the drive transistor 1 and the first transistor 2A
and the base potential of second transistor 2B is lowered, and these transistors 1 and 2A.

The base potential of 2B is clamped to a potential obtained by subtracting the forward voltage drop of diode 2D from VEEI, and is controlled to be in an off state.

Since the driving transistor 1 and the first transistor 2A constituting the current mirror circuit 2 are controlled to be in an OFF state, the impedance seen from the load 3 side appears to be in a high impedance state.

Therefore, for example, in an IC test device, the load 3 is
In the case of C, the driving transistor and the first transistor 2A can be controlled to the OFF state by applying H logic to the input terminal ENI and applying L logic to EN2 at the timing when the IC under test outputs a signal. By operating a signal acquisition circuit (not particularly shown) for acquiring a signal in this state, the signal output from the load 3 can be effectively acquired into the signal acquisition circuit.

Note that diodes 8 and 9 shown in FIG. 4 are diodes connected to reduce the value of output capacitance.

FIG. 5 shows an embodiment of the fourth invention and the fifth invention of this application. A fourth invention of this application proposes a configuration in which a potential absorption transistor 11 is connected in series between the drive transistor 1 and the first transistor 2A forming the current mirror circuit 111i2.

By applying an appropriate forward bias (2) to the base of this potential absorption transistor 11, when the electric potential of the drive transistor 1 fluctuates in response to a human input signal, the potential absorption transistor 11 The resistance value between the collector and base of the transistor 11 changes, absorbing potential fluctuations, and operates to maintain the potential of the collectors of the two first transistors constituting the current circuit 2 at a constant potential.

In this way, by operating the collector potential of the first transistor 2A at a constant potential, the first
It is possible to prevent charging and discharging current from flowing into the collector-base capacitance ICCE of the transistor 2A.

As a result, there is an advantage that the operating speed of the current mirror circuit 2 can be improved.

In other words, the first transistor 2A has a current charger circuit lS
In order to obtain a large current ratio of 2, a large number of transistors are connected in parallel.

For this reason, the value 9 of the collector-base capacitance CCB becomes a large value. When the value of the collector-base capacitance C6B is large and the potential absorption transistor 11 is not provided, when the industrial voltage potential of the drive transistor 1 changes, the collector potential of the first transistor 2A also changes.

When the collector potential of the first transistor 2A fluctuates, a charge-discharge current flows through the collector-base capacitor C6B in accordance with the collector potential fluctuation. The output current I is caused by the flow of this charging and discharging current. It takes time for ut to stabilize, causing a response delay. In other words, the upper limit of the response speed is determined by the time constant of the time constant circuit formed by the collector-base capacitance.

Therefore, the response speed of the amplifier can be improved by maintaining the collector potential of the first transistor 2A constant by the potential absorbing transistor 11 and preventing charging/discharging current from flowing through the collector-base capacitance CCB.

In FIG. 5, the second
A series connection circuit 12 of diodes connected between the collector and the base of the transistor 2B refers to a constant voltage element proposed in the fifth invention of this application.

A fifth invention of this application proposes a configuration in which a constant voltage element 12 is connected between the collector and base of the second transistor 2B that constitutes the current mirror circuit 2.

By providing this constant voltage element 12, the collector-emitter voltage VCE of the second transistor 2B can always be ensured. As a result, the second transistor 2
It is possible to prevent the charging/discharging voltage from flowing to the collector-emitter capacitance cci of B. Therefore, the operation of the second transistor 2B can be made faster.

"Effect of the invention" As explained above, according to the first invention of this application, NP
Even though the amplifier circuit is constructed using only N-type transistors, the drive transistor 1 and the first transistor 2A that constitutes the current mirror circuit 2 operate complementary to each other, and can output a large-amplitude current with low power consumption. .

Furthermore, according to the second invention of this application, by increasing the current ratio between the current mirror circuits 2 and 5, it is possible to reduce the current value flowing through the drive transistor 1 during no load. As a result, there is an advantage that the power consumption of the amplifier proposed in the first invention can be further reduced.

Further, according to the third invention of this application, a switch element 6 is provided on the input side of the drive transistor 1, and by turning on/off the switch element 6, the drive transistor 1 is connected in series with the drive transistor 1. The first transistor 2A constituting the current mirror circuit 2 can be controlled to be in an OFF state. Therefore, by controlling this state, the impedance seen from the load 3 side can be brought into a high impedance state, and the load 3
The signal output from the load 3 can be effectively captured into the signal capture circuit connected to the load 3.

Furthermore, according to the fourth invention and the fifth invention of this application,
Since the response speed of the current mirror circuit 2 can be improved, it is possible to provide an amplifier that can amplify and output a high frequency signal.

Modified Embodiment A modified embodiment of the present invention is shown in FIG.
A case is shown in which the current mirror circuit 2 is controlled via the transistor 14 constituting the emitter follower.

[Brief explanation of drawings]

FIG. 1 is a connection diagram for explaining in detail the first invention of this application, FIGS. 2 and 3 are connection diagrams for explaining in detail the second invention of this application, and FIG. 4 is a connection diagram for explaining in detail the second invention of this application. 5 is a connection diagram for detailed explanation of the fourth invention and the fifth invention of this application, and FIG.
The figure is a connection diagram for explaining a modified embodiment of the first invention of this application, and FIG. 7 is a connection diagram for explaining a conventional technique. 3 1: Drive transistor, 2: Current mirror circuit, 2A
:first transistor, 2B=second transistor, 2C:
Voltage shifter, 3: load, 4: constant current circuit, 5: current mirror circuit. 4

Claims (5)

[Claims] (1) A: an NPN type drive transistor constituting an emitter follower; B: a constant current circuit connected to the collector side of this drive transistor; C: a first transistor connected in series with this drive transistor; a current mirror circuit configured by a second transistor whose base and collector are commonly connected to the base of the transistor, and whose common contact point between the base and collector is connected to the connection point between the constant current circuit and the drive transistor through a voltage shifter; An amplifier constructed by (2) The current mirror circuit according to claim (1), wherein a plurality of first transistors that draw the current flowing through the drive transistor are connected in parallel. (3) In the amplifier according to claim (1), by providing a switch element on the input side of the drive transistor and controlling this switch element to a short-circuited state as necessary,
An amplifier characterized in that the drive transistor is controlled to a cut-off state and the output impedance is maintained at high impedance. (4) In the amplifier according to claim (1) or (2), a potential absorption transistor is connected in series between the emitter of the drive transistor and the collector of the first transistor constituting the current mirror circuit, and the current mirror 1. An amplifier characterized in that the amplifier is configured to maintain a constant potential at the collector of a first transistor constituting the circuit. (5) In the amplifier according to claim (1) or (2), a constant voltage element is provided between the collector and the base of the second transistor constituting the current mirror circuit for maintaining the collector-base potential at a constant value. An amplifier characterized in that it is connected.