JPH0528127U - Current switch circuit - Google Patents

Abstract

(57) [Summary] [Object] To realize a current switch circuit with a small output current Ip, a small switching current Ip, and a large output current waveform with a small ringing in an optical communication transmitter and the like over a wide current range. [Configuration] When the switching current Ip becomes large, Tr
34 increases the amplitude of the output voltage of the switch drivers 35 and 36 that drive the Trs 31 and 32. Further, when the temperature rises, the constant current source Ic having a positive temperature coefficient increases the amplitude of the output voltage of the switch drivers 35 and 36. As a result, the switching speed of the Trs 31 and 32 can be kept constant and the occurrence of Ip ringing can be minimized even when the temperature changes from a small Ip to a large Ip.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a current switch circuit for driving a load such as a light source such as a light emitting diode (hereinafter referred to as LED) or a laser diode (hereinafter referred to as LD) in a transmitter for optical communication.

[0002]

[Prior Art]

Conventionally, as a technique in such a field, there has been one described in the following documents, for example. Reference 1: Technical Report of IEICE (Technical Report), 89 [226] (19 89) Kijima et al., "Optical Transceiver for Wideband LSDN Subscriber System (OCS89-34)" p. 7-13 Reference 2: Japanese Patent Application Laid-Open No. 1-245582 As described in References 1 and 2, for example, an LED or LD is generally used as a light source in optical communication, and an emitter-coupled drive is used to drive the LED or LD.・ A lot of logic (ECL) type current switch circuits are used. An example of the configuration is shown in FIGS.

2 and 3 are circuit diagrams showing a configuration example of a conventional current switch circuit. The current switch circuit of FIG. 2 is an unbalanced input type circuit that drives a light source D composed of an LED or an LD, and is an NPN type transistor (hereinafter, referred to as Tr) 1, 2 ,, which constitutes an ECL type current switch. 3, an external emitter resistor 4 of the ECL sink current Tr3, and a DC bias current source Ib of the light source D. In FIG. 2, Ccb is the collector-base capacitance of Tr3 for ECL sink current, Cs is the collector-ground stray capacitance of Tr3, and Vp is the base bias power supply of Tr3. The DC bias current source Ib of the light source D is generally unnecessary (Ib = 0) when the light source D is an LED.

Since this current switch circuit is of an unbalanced input type, the transmission pulse signal source S of ECL logic level is applied to the base of Tr1 and the reference power supply Vr for giving the threshold level of ECL is applied to the base of Tr2. Apply. The switching current Ip flowing through Tr1, 2 is controlled by the base bias power supply Vp and the emitter resistor 4. When the potential of the signal source S is higher than the potential of the reference power source Vr (logic “H”), the light source D is turned on, and conversely, when it is low (logic “L”), it is turned off.

The current switch circuit of FIG. 3 is a balanced input type circuit, and is configured to apply a negative-phase signal source r of the transmission pulse signal source S to the base of Tr 2 instead of the reference power source V r. .

In this current switch circuit, similarly to the circuit of FIG. 2, when the potential of the signal source S is higher than the potential of the negative phase signal source r (logic “H”), the light source D is turned on, and conversely low. In the case (logic "L"), it is turned off.

[0007]

[Problems to be solved by the device]

 However, the conventional current switch circuit has the following problems. (A) FIG. 4 is a waveform diagram of the switching current Ip in the current switch circuit of FIG.

In the current switch circuit of FIG. 2, when the signal source S changes “1” or “0”, the collector potential of Tr 3 also changes at the same time, and the charge / discharge currents of the capacitors Ccb and Cs are generated. Considering the transient state of the light source D from the off state to the on state, as shown in FIG. 4, the switching current Ip (steady Ip) determined by the base bias power supply Vp and the emitter resistor 4 is initially charged to the charging current of the capacitors Ccb and Cs. Since Ip1 is added, the current once becomes a large current, and then the discharge current Ip2 corresponding to the overcharge of the capacitances Ccb and Cs is negatively changed to a small current. Then, at the end of charging / discharging, the steady Ip is finally reached. Therefore, the waveform of the switching current Ip becomes a waveform including ringing.

The absolute value of the ringing current component depends on the values of the capacitors Ccb and Cs and the variation of the collector potential of Tr3 (generally the magnitude of the input amplitude), regardless of the magnitude of the steady Ip. In a light source drive for optical communication, a current range of Ip = 5 to 100 mA is used. For example, when the allowable current value is large (Tr3 size is large and the capacitances Ccb and Cs are large) such that Ip (max) = 100mA and operation Ip = 10mA, and the actual operation current is small, the ringing current component for the steady Ip is small. May exceed 200% (peak value ratio).

(B) In the current switch circuit of FIG. 3, the reference power source Vr is replaced with a signal source r having a phase opposite to that of the transmission pulse signal source S, and a balanced input system is adopted. Therefore, the fluctuation of the collector potential of Tr3 during the transition is smaller than that of the circuit of FIG. 2, and the ringing amount is reduced. However, since the transient response speeds of ECL on and off are generally different, the transmission pulse signal source S and the anti-phase signal source r do not become exactly in anti-phase, and a considerable amount of ringing remains.

The ringing of the switching current Ip of the optical communication transmitter disturbs the transmitted light waveform and causes malfunctions such as a malfunction of the automatic power control of the light source D and an increase in the error rate on the receiving side. Therefore, conventionally, the signal pulse width is made long enough to make ringing negligible (constant speed operation), or used only in the vicinity of Ip (max) where ringing is not noticeable (narrow Ip range). In either case, the speedup and generalization (realization of a wide Ip range) were greatly restricted by that. Therefore, it has been difficult to provide a current switch circuit which is technically sufficiently satisfactory.

The present invention provides a current switch circuit, which solves the problem that the above-mentioned prior art has, that it is difficult to reduce the ringing of the output current without lowering the response speed.

[0013]

[Means for Solving the Problems] In order to solve the above problems, a first invention is to turn on a current switch circuit such as a transmitter for optical communication according to a potential difference between a first node and a second node, A differential switch circuit that has first and second Trs that are turned off to switch the power supply current and that supplies the power supply current to a load such as a light source, the first and second Trs, and a third node A first resistor connected in series between the first resistor and a second resistor, a base connected to the first current control terminal, and a first resistor connected in series between the third node and the second current control terminal. 3 Tr and the base are connected to the first current control terminal, and are connected in series between the fourth node and the second current control terminal to form a current mirror circuit together with the third Tr. And a fourth Tr to be formed.

Further, first and second collector resistors respectively connected to a power source, and bases respectively connected to the first and second input terminals, the first and second collector resistors and the fourth collector resistor respectively. A switch driver comprising fifth and sixth Trs connected in series with a node and supplying output voltages to the first and second nodes, respectively, and having a temperature-dependent characteristic A first constant current source that is connected and supplies a constant current to the fifth and sixth Tr 2 is provided.

Then, the collector currents of the third and fourth Trs are controlled by using the first and second current control terminals, and a signal source is connected to the first input terminal. , A reference power source or a negative phase signal source corresponding to the signal source is connected to the second input terminal.

According to a second invention, in the current switch circuit according to the first invention, first and second transistors connected between the first and second nodes and the first and second Trs, respectively. A base resistance, first and second stabilizing resistances respectively connected between the third and fourth Tr and the second current control terminal, and a fifth resistance and a sixth Tr. Buffer and level shifting seventh and eighth Trs for transmitting output voltage to the first and second nodes, respectively, and second and third Trs for supplying constant currents to the seventh and eighth Trs, respectively. Three constant current sources and first and second buffer resistors are provided.

According to a third aspect of the invention, in the second aspect, the currents when the first and second Trs are on and off are Ip (on) and Ip (off), respectively, and the electron charge is q. When the Boltzmann constant is k, the absolute temperature is T, the emitter area of the third Tr is A3, the emitter area of the fourth Tr is A4, and the grounded-emitter current amplification factor of those Tr is HFE, By setting the values of K1, K2, and K3 based on the equation, the dependence of the drive factor m on the current and temperature is controlled. n = A3 / A4 = second stabilizing resistance / first stabilizing resistance Ip (on) >> Ip (off), Ip≈Ip (on) m = Ln (Ip (on) / Ip (off)) ( However, Ln (); natural logarithm) Rc = first collector resistance = second collector resistance, Re = first resistance = second resistance Rb = first base resistance = second base resistance (Rc / N-Re-Rb / (1 + HFE)) = K1 Rc * Ic-m * k * T / q = K2 (however, *; multiplication) Δ (Rc * Ic-m * k * T / q (ΔT) = K3

[0018]

[Action]

 In the conventional current switch circuit, the amplitude of the drive voltage that drives the first and second Tr 1 that constitutes the differential switch circuit is constant. If the value of the switching current by the differential switch circuit is small, switching is possible even if the amplitude of the drive voltage of the differential switch circuit is small, but if the switching current becomes large, the amplitude of the drive voltage becomes large. Without it, it does not switch. That is, the amplitude of the drive voltage required for switching depends on the switching current and temperature. However, in the conventional switching circuit, the amplitude of the drive voltage for driving the differential switch circuit has to be set to a large value in accordance with the large switching current value. Therefore, when the switching current value is small, the amplitude value of the drive voltage is too large, which causes a disadvantage that a large ringing occurs in the switching current.

Therefore, in order to solve such inconvenience, in the current switch circuit of the first invention, the drive voltage level of the first and second Trs proportional to the switching current flowing in the differential switch circuit is set to the first The transistor Tr4 causes the switch driver to generate and supply it to the first and second nodes. When the first constant current source has, for example, a positive temperature characteristic, the switch driver generates the drive voltage levels of the first and second Trs according to the temperature rise. That is, when the switching current increases, the amplitude of the drive voltage of the first and second Trs is increased by the fourth Tr. Further, when the temperature rises, the first constant current source increases the amplitudes of the drive voltages of the first and second Trs.

In this way, the amplitude of the output voltage of the switch driver that drives the differential switch circuit changes to an optimum value according to the value of the switching current and the temperature, and the differential switch circuit is always kept at the optimum level. Can be switched. This makes it possible to realize a current switch with a small switching current, a large switching current, and a small switching current ringing and a fast response speed even when the temperature changes.

In the second invention, the first and second base resistors and the first and second resistors of the first invention are the internal base resistance and internal emitter ohmic resistance of the first and second Trs themselves. It works so as to ignore the resistance and further controls the dependence of the drive factors of the first and second Trs on the switching current. In other words, the switching current dependence coefficient of the drive factor can be made positive or negative by selecting the first and second base resistors and the first and second resistors. Here, the drive factor can be represented by (drive factor) = Ln (Io (ON) / Io (OFF)). And when the drive factor is large, the switching is fast, but the ringing is large. Conversely, when the drive factor is small, switching is slow, but ringing is small. Also, the first and second stabilizing resistors stabilize the mirror current ratio formed by the third and fourth transistors.

In the third invention, by setting the values of K1, K2 and K3 arbitrarily, it is possible to control the dependence characteristic of the drive factor on the switching current and the temperature. Therefore, the above problems can be solved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a circuit diagram of a current switch circuit showing a first embodiment of the present invention. This current switch circuit is a circuit for driving a light source D of an LED or an LD, a first input terminal 11 to which a transmission signal source S is connected, a reverse phase signal source r of the transmission signal source S, or the transmission signal source. It has the 2nd input terminal 12 to which the reference power supply Vr corresponding to S is connected, the 1st, 2nd current control terminals 21 and 22, and the 1st-8th Tr31-38 of NPN type. The first and second Trs 31 and 32 form a differential switch circuit, the third and fourth Trs 33 and 34 form a current mirror circuit, and the fifth and sixth Trs 35 and 36 form a switch driver. Further, the seventh and eighth Trs 37 and 38 have a buffer / level shift function.

A first base resistor 41 is connected between the first node N1 and the base of the first Tr31, and a second base resistor 41 is also connected between the second node N2 and the base of the second Tr32. The base resistor 42 is connected. The positive power source + V is connected to the collector of the first Tr 31 via the light source D, and the positive power source + V is connected to the collector of the second Tr 32. The emitters of the first and second Trs 31 and 32 are commonly connected to the third node N3 via the first and second resistors 51 and 52. The third Tr 33 and the first stabilizing resistor 61 are connected in series between the third node N3 and the second current control terminal 22, and the fourth node N4 and the second current control terminal 22 are further connected. The fourth Tr 34 and the second stabilizing resistor 62 are connected in series between and.

The third Tr 33 allows a switching current Ip to flow through the first and second Trs 31 and 32 that form a differential switch circuit, and the fourth Tr 34 includes the fifth and sixth Trs that form a switch driver. It is a transistor that causes a current Ip / n proportional to the switching current Ip to flow through the transistors 35 and 36. The bases of the Trs 33 and 34 are commonly connected to the first current control terminal 21. The first and second stabilizing resistors 61 and 62 are resistors for stably operating the current mirror circuit, and can be omitted when the area ratio of the third Tr 33 and the fourth Tr 34 is close to 1. Is.

A control voltage source is connected between the first and second current control terminals 21 and 22, or an appropriate DC voltage Vp is applied to the first current control terminal 21, and The control current source Ipc is connected to the current control terminal 22 of No. 2 to set the required switching current Ip.

The first and second input terminals 11 and 12 are connected to the bases of the fifth and sixth Trs 35 and 36 that form a switch driver, and the collectors of the Trs 35 and 36 are connected to collector resistors 71 and 36, respectively. Each of them is connected to the positive power source + V via 72. The emitters of the fifth and sixth Trs 35 and 36 are commonly connected to the fourth node N4, and a constant current Ic0 is supplied to the Trs 35 and 36 between the node N4 and the negative power supply -V. Therefore, a first constant current source Ic having a positive temperature dependence characteristic is connected.

To the collectors of the fifth and sixth Trs 35 and 36, the bases of the seventh and eighth Trs 37 and 38 for buffering and level shifting are connected. The Trs 37 and 38 are transistors that connect the switch driver and the differential switch circuit. The collectors of the Trs 37 and 38 are connected to the positive power source + V, and the emitters are connected to the second and first nodes N2 and N1. Each is connected. Between the second and first nodes N2 and N1 and the negative power source -V, constant current sources IL1 and IL2 for smoothly performing the off operation of the first and second Trs 31 and 32 are connected, respectively. ing. The second and third constant current sources IL1 and IL2 may be replaced with resistors.

In this current switch circuit, if a negative-phase signal source r is connected to the second input terminal 12, a balanced input method is used, and if a reference power source Vr corresponding to the transmission signal source S is connected, an unbalanced input method is used. It becomes the circuit of.

Next, the operation will be described. When this current switch circuit is provided in, for example, a transmitter for optical communication, this transmitter for optical communication is 1/100 or less of the ON operation side on the OFF operation side of Tr31 and 32 which configure the differential switch circuit. Even if a small amount of electric current is flowing, there is no practical problem. It is assumed that the Tr31 turns on and the switching current Ip (on) flows, and the Tr32 barely turns off and a minute current Ip (off) flows. The collector current Icc of Tr is given by the following equation (1), where Vbe is the base-emitter voltage, Is is the reverse saturation current of Tr, Is is the electron charge, k is the Boltzmann constant, and T is the absolute temperature. Can be similar. Icc = Is * exp (q * Vbe / k / T) (1) However, *; The grounded emitter current amplification factor of the multiplication Tr is HFE, Rc = first collector resistance 71 = second collector resistance 72 , Re = first resistor 51 = second resistor 52, Rb = first base resistor 41 = second base resistor 42, Ip (on) >> Ip (off), Ip≈Ip (on), and m = Ln (Ip (on) / Ip (off)) (2) where Ln (); natural logarithm, the potential difference V12 between the first and second nodes N1 and N2 is V12 = Ip * (Re + Rb / (1 + HFE)) + m * k * T / q (3)

When k * T / q≈26 mV and Ip (on) / Ip (off) = 100 to 1000, the value of (m * k * T / q) in the equation (3) is about 120 mV to 180 mV. .. Even with Ip (on) / Ip (off) = 10000, it is about 240 mV.

In the current mirror circuit composed of the third and fourth Trs 33, 34 and the first and second stabilizing resistors 61, 62, the area ratio of Tr 33 and Tr 34 and the stabilizing resistors 61, 62 are shown. When the resistance ratio is set as follows: n = (emitter area ratio of Tr33) / (emitter area ratio of Tr34) = stabilizing resistor 62 / stabilizing resistor 61 (4) The switching current Ip flows through the Tr33. Then, the current flowing through Tr34 becomes (Ip / n). Therefore, the current Ico flowing through the switch driver composed of the Trs 35 and 36 is expressed by the following equation (5). Ico = Ic + Ip / n (5) Further, the output amplitude voltage V0 of the switch driver constituted by the Trs 35 and 36 is V0 = Rc * Ico = Rc * (Ic + Ip / n) (6) .. From the circuit operation, since the output amplitude voltage V0 is equal to the voltage V12 between the first and second nodes N1 and N2, the following equations (7) and (8) are established. V0-V12≈0 (7) V0-V12 = Rc * (Ic + Ip / n) -Ip * (Re + Rb / (1 + HFE))-m * k * T / q = Ip * (Rc / n-Re- Rb / (1 + HFE)) + ( Rc * Ic-m * k * T / q ) (8) If the first term of the equation (8) is independently "≈0", Ip changes. M is not affected. If the second term of the equation (8) is independently “≈0” with m being a constant value, m will not be affected even if the temperature changes. If both the first term and the second term are “≈0”, m can be kept constant with respect to changes in Ip and changes in temperature. These relationships are shown in the following equations (9) to (11). Rc / n-Re-Rb / (1 + HFE) ≈0 (9) (1st term≈0) Rc * Ic-m * k * T / q≈0 (10) (Second at room temperature Item ≈0) Δ (Rc * Ic-m * k * T / q) / (ΔT) ≈0 That is, Δ (Rc * Ic) / (ΔT) -m * k / q≈0 (second term temperature odor) Distribution ≈ 0) (11) If the values of the internal base resistance and internal emitter ohmic resistance of Tr31 and 32 are added to Rb and Re, respectively, and equations (9) to (11) are satisfied, ideal Be in shape. The absolute value of (m * k / q) in the equation (11) is around 0.5 mV / ° C, and the constant current source Ic having the same temperature gradient of (Rc * Ic) is a bandgap power source and a transistor. It can be easily realized by combining the above.

By making the expression (9) positive, it is possible to increase m as Ip increases. If the external resistances Rc, Rb, and Re are made relatively large, the base resistance and emitter ohmic resistance inside Tr can be ignored. By appropriately setting the temperature coefficient of the constant current source Ic, m can be changed appropriately with respect to the temperature. As described above, by freely setting the values of the expressions (9) to (11), it is possible to control the switch drive factor with respect to Ip and temperature change (control of the m value). The first embodiment has the following advantages.

From a small switching current Ip to a large switching current Ip, over a wide range of switching current Ip, it is possible to always realize a current switch with small ringing. For example, if the conventional device shown in FIG. 2 and the device shown in FIG. 1 of the first embodiment are configured with the same elements and the simulation comparison is performed, in order to suppress the ringing component of Ip to be 15% or less of the steady Ip, While the conventional circuit of FIG. 2 has an Ip range of Ip (max) to Ip (max) / 2, the circuit of FIG. 1 of the present embodiment has Ip (max) to Ip (max) / 20. , The variable range of about one digit Ip is widened.

Therefore, when the current switch circuit of the present embodiment is used in, for example, an LED driver or an LD driver for optical communication, the optical waveform of the transmitter is improved, and stable transmitter auto power control is realized. Also, high quality reception with a small error rate becomes possible. Furthermore, since the signal pulse width can be shortened to the very end of the ringing convergence time, a high-speed optical transmitter can be realized. Moreover, it is possible to realize a highly versatile optical transmitter (a wide range of switching current Ip) that can be applied to various LDs and LEDs.

5 to 8 are circuit diagrams of the current switch circuits according to the second to fifth embodiments of the present invention.

Second Embodiment In the current switch circuit of FIG. 5, the seventh and eighth Trs 37, 38 are added by adding a resistor 73 for level shift so as to cope with the light source D having a large voltage drop when turned on. Level shift the emitter potential of. The first and second constant current sources IL1 and IL2 of the buffer transistors 37 and 38 are replaced with the first and second buffer resistors 81 and 82. Then, a DC bias source Ib is added to the light source D, and the switching current Ip is controlled by the first current control terminal 21 on the base side of the third and fourth TRs 33 and 34.

With this configuration, the resistance 73 for level shift can prevent saturation of the first Tr 31 and the like, and an accurate current switch can be performed.

Third Embodiment In the current switch circuit of FIG. 6, a diode 74 is used in place of the resistor 73 in the current switch circuit of FIG. 5 for level shifting. A constant current source IL is added to the buffer resistors 81 and 82 to form a hybrid circuit. A resistor 63 is added between the second current control terminal 22 and the negative power source -V. Then, a part of the light output of the light source D constituted by the LD is received by the back light detector 90 such as a light receiving diode (hereinafter referred to as PD), and the switching current Ip and the output current Ib of the collector of the Tr31 are controlled. An auto power control circuit 91 is added.

With such a configuration, as in the case of FIG. 5, accurate current switching can be performed, and since the automatic power control circuit 91 is added, the fluctuation of the light source D can be controlled.

Fourth Embodiment In the current switch circuit of FIG. 7, a resistor 63 is connected between the second current control terminal 22 and the negative power source −V in the current switch circuit of FIG. 1 to control the switching current Ip. Is performed at the first current control terminal 21. Level shift is performed by adding buffer resistors 81 and 82 to the respective emitters of the seventh and eighth Trs 37 and 38. Tr101 and 102 whose power supply Vd1 is commonly connected to the base are connected in series to the collectors of the first and second Tr31 and 32, respectively, and Tr103 and 104 whose base is commonly connected to the power supply Vc are the third and third. 4 are connected in series to nodes N3 and N4, respectively, and Tr105 and 106 whose bases are commonly connected to the power supply Vd2 are connected in series to the collector side of the fifth and sixth Trs 35 and 36.

With such a configuration, the precision of the mirror current value and the switching speed can be improved.

Fifth Embodiment In the current switch circuit of FIG. 8, in the current switch circuit of FIG. 1, the first and second constant current sources IL1 and IL2 are connected to the first and second base resistors 81 and 82, respectively. It is replaced with a hybrid circuit with the constant current source IL, and diodes 111 and 112 are added to the emitters of the seventh and eighth Trs 37 and 38, respectively, to perform level shift. A resistance 63 is provided between the second current control terminal 22 and the negative power source -V, and the switching current Ip is controlled by the first current control terminal 21. Then, the circuit is replaced as shown in FIGS. 9 (a) and 9 (b).

That is, FIGS. 9A and 9B are partial circuit diagrams in FIG. As shown in FIG. 9 (a), the T-shaped circuit composed of the resistors 51, 52, 61 and Tr33 of FIG. 1 is replaced with resistors 51, 52, 61-1, 61 as shown in FIG. 9 (b). -2 and Trs 33-1 and 33-2 are replaced with a? -Type circuit. The resistors 51 and 52 have the same resistance value, and the resistors 61-1 and 61-2 have a resistance value twice that of the resistor 61. When the emitter size of Tr 33 is A3, the emitter sizes of Tr 33-1 and 33-2 are set to A3 / 2.

With such a configuration, a DC current does not flow through the resistors 51 and 52, and thus there is an advantage that the saturation of the Tr3 3-1 and the Tr 33-2 can be prevented.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the current switch circuits of the first to fifth embodiments, the NPN type Tr is used, but they may be configured by other transistors such as PNP type Tr and field effect Tr. When the PNP type Tr is used, the voltage and current, the polarity of the connecting diode, and the like may be reversed. The automatic power control circuit 91 of FIG. 6 in the third embodiment can be provided in other embodiments. Further, the above embodiment can be applied to loads other than the light source.

[0047]

[Effect of the device]

 As described in detail above, according to the first invention, a current switch having a small ringing can be always performed over a wide range of output currents from a small output current to a large output current. Since the ringing level can be reduced, the signal pulse width can be shortened to the very end of the ringing convergence time, and the operating speed can be increased. Since the ringing can be reduced over a wide output current range, the versatility that can be used to drive various light sources is expanded.

According to the second invention, since the first and second stabilizing resistors are provided, the current mirror circuit can be stably operated. Moreover, the second and third constant current sources or the first and second buffer resistors can smoothly operate, for example, the OFF operation of the first Tr and the second Tr.

According to the third invention, by setting the values of K1, K2, and K3 arbitrarily, the switch drive factor with respect to changes in output current and temperature can be controlled, and a more accurate current switch can be obtained. Is possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a current switch circuit showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional current switch circuit.

FIG. 3 is a circuit diagram of a conventional current switch circuit.

FIG. 4 is a waveform diagram of the switching current Ip of FIG.

FIG. 5 is a circuit diagram of a current switch circuit showing a second embodiment of the present invention.

FIG. 6 is a circuit diagram of a current switch circuit showing a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a current switch circuit showing a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of a current switch circuit showing a fifth embodiment of the present invention.

9 is a partial circuit diagram in FIGS. 1 and 8. FIG.

[Explanation of symbols]

 11, 12 1st, 2nd input terminal 21, 22 1st, 2nd current control terminal 31-38 1st-8th Tr 41, 42 Base resistance 51, 52 1st, 2nd resistance 61, 62 1st, 2nd stabilizing resistance 71, 72 1st, 2nd collector resistance Ic, IL1, IL2 1st-3rd constant current source Ip switching current Ipc control current source D light source + V positive power supply -V negative Power supply

Claims (3)

[Scope of utility model registration request] 1. A differential switch having first and second transistors that switch a power supply current by performing on / off operations according to a potential difference between a first node and a second node, and supply the power supply current to a load. A circuit, first and second resistors connected in series between the first and second transistors and a third node, and a base connected to a first current control terminal, A third node connected in series between the node and the second current control terminal
And a base connected to the first current control terminal, and a base
A fourth transistor that is connected in series between the second node and the second current control terminal to form a current mirror circuit with the third transistor, and first and second collector resistors that are connected to a power supply, respectively. And the base is connected to the first and second input terminals, respectively,
A switch driver including fifth and sixth transistors connected in series between the first and second collector resistors and the fourth node to supply an output voltage to the first and second nodes, respectively. A first temperature-dependent characteristic that is connected to the fourth node and supplies a constant current to the fifth and sixth transistors;
And a configuration in which the collector currents of the third and fourth transistors are controlled by using the first and second current control terminals, and the signal source is connected to the first input terminal. A current switch circuit, characterized in that a reference power source or a negative phase signal source corresponding to the signal source is connected to the second input terminal. 2. The current switch circuit according to claim 1, further comprising: first and second base resistors connected between the first and second nodes and the first and second transistors, respectively. The output voltages of the first and second stabilizing resistors respectively connected between the third and fourth transistors and the second current control terminal and the output voltages of the fifth and sixth transistors are set to the first
Buffer and level shifting seventh and eighth transistors respectively transmitting to the second and third nodes, and second and third constant current sources or third constant current sources for supplying constant currents to the seventh and eighth transistors, respectively. A current switch circuit comprising: a first buffer resistor; and a second buffer resistor. 3. The current switch circuit according to claim 2, wherein the on-state and off-state currents of the first and second transistors are Ip (on) and Ip (off), respectively, and the electron charge is q, The Boltzmann constant is k, the absolute temperature is T, the emitter area of the third transistor is A3, and the fourth transistor is the fourth area.
When the emitter area of each transistor is A4 and the grounded-emitter current amplification factor of those transistors is HFE, by setting the values of K1, K2, and K3 based on the following formulas, the drive factor m with respect to the current and temperature is set. A current switch circuit having a structure for controlling a dependence characteristic. n = A3 / A4 = second stabilizing resistance / first stabilizing resistance Ip (on) >> Ip (off), Ip≈Ip (on) m = Ln (Ip (on) / Ip (off)) ( However, Ln (); natural logarithm) Rc = first collector resistance = second collector resistance, Re
= First resistance = Second resistance Rb = First base resistance = Second base resistance (Rc / n-Re-Rb / (1 + HFE)) = K1 Rc * Ic-m * k * T / q = K2 (however, *;
Multiplication) Δ (Rc * Ic-m * k * T / q (ΔT) = K3