JPS60107794A - Current switching circuit - Google Patents

Abstract

PURPOSE:To prevent overshoot and ringing of a current of a transistor (TR) switched from nonconduction to conduction by inserting a resistor between an emitter of the TR of a current switching circuit of a semiconductor memory and a current supply line. CONSTITUTION:In applying the circuit to a sense circuit, resistors 21-28 for current damping between the emitter of the current switching TR and the current source are connected in series and when the said TR is switched from nonconduction to conduction, the flowing of the charging current to parasitic capacitors Cs1-Cs3 is suppressed from being flowed rapidly. Thus, the overshoot of the current of the said TR is small and the ringing is less and sense output voltages VSG, V'SG are voltages with small oscillation. Moreover, the oscillation of digit line clamp voltages Vc, Vc' is small and the undershoot is small and then the saturation of a TR11 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a current switching circuit for a bipolar semiconductor device.
and a current switching circuit suitable for preventing ringing.

[Background of the invention]

As an example of a current switching circuit for a bipolar semiconductor device, there is a sense circuit for a semiconductor memory shown in FIG. In FIG. 1, 1 is a word line, 2 is a digit line, 3 is a memory cell, 4 is a current source for holding information, 5 is a current source for clamping the digit line, and 6 is a current source for reading. The emitter is connected to each digit line, and the transistor 13
A reference voltage is applied to the transistors 14 and 14, and the collectors of these transistors are connected in common, and are connected to the emitters of transistors 14 and 15, respectively, forming a wired-OR connection. Also, 7 to 12 are each de
This is a transistor for selecting the f-bit line pair. According to this circuit, the read current flows through the memory cell and either transistor 14 or 15 depending on the information of the selected memory cell. Therefore, a potential difference is generated between the sense output signal lines 16 and 17, and memory information is outputted via the differential amplifier 18.

Next, the drawbacks of this circuit will be explained. The digit line selection signal Vy1 is switched from high potential (High) to low potential (LOW).
When K is switched, the read current flowing from transistors 7 and 9 is cut off, and begins to flow from transistors 10 and 12. At this time, if the read current changes as shown by the broken line in Figure 3, there is no problem, but ■! 2 switches from LOW to HIGH, the parasitic capacitance Cms is photoelectrically charged, resulting in a current with an overshoot as shown by the solid line in FIG. 3, and then ringing occurs as in the emitter-follower linking phenomenon. As mentioned above, the sensing method for information stored in a memory cell is such that the read current is passed through the transistor 14.
For example, the read current with large oscillations accompanied by linking is passed through either transistors 10 and 15 and creates a potential difference in the sense output signal line.
3 to the transistor 14, the voltage (Vsa) of the sense output signal line 16 oscillates as shown by the solid line in FIG. Such a vibrating signal distorts the output waveform of the differential amplifier 18, thereby interfering with normal operation. Further, since the read current also flows to the memory cell, it also causes the information in the memory cell to be inverted.

Yet another problem is that when the digit line clamping current is switched from transistor 8 to transistor 11, the parasitic capacitance Cl1
In order to charge zt, a current flows through the transistor 11 with an automatic shoot and ringing as shown by the solid line in FIG. 3 in the same way as the read current. Therefore, the voltage (Vc) of the digit line Lanzo signal line 19 becomes as shown by the solid line in FIG. 5, and the transistor 11 becomes saturated.
Vc may oscillate, causing memory malfunction.

[Purpose of the invention]

An object of the present invention is to provide a % optical switching circuit for a semiconductor memory.
An object of the present invention is to provide a current switching circuit that prevents overshoot and ringing of the current of a transistor that switches from non-conductive to conductive.

[Summary of the invention]

In a current switching circuit, the overshoot of the current of a transistor that switches from non-conducting to conducting is due to the parasitic capacitance i.
This is because charging to t Cm is done rapidly, so
Overshoot can be reduced by charging the parasitic capacitance it Cm more slowly. Generally speaking, it is known that one way to slow down the charging of a capacitor is to insert a resistor between the power transmission end and the capacitor, and this was applied.

[Embodiments of the invention]

Hereinafter, as an embodiment of the present invention, an example of application to a memory sense circuit will be described with reference to FIG.

Drawing numbers 1 to 20 correspond to FIG. 1, and resistors 21 to 28 are current damping resistors that are a feature of the present invention. This resistor is connected in series between the emitter of the current switching transistor and the current source. This prevents the charging current from flowing steeply to the parasitic capacitors (061 to Csa) when the capacitance is turned off.

Therefore, the current of the % current switching transistor has a small overshoot as shown by the broken line in Fig. 3, and a current with a small S/King.
) becomes a voltage with small oscillations as shown by the broken line in FIG. Further, the digit line clamp voltages (Vc, Vc) have small vibrations as shown by the broken line in FIG. 5, and have small undershoots, so that saturation of the transistor 1 is also prevented.

Note that the damping resistor should be placed very close to the emitter of the current switching transistor. If a capacitance is inserted between the emitter and the damping resistor, the effect of the damping resistor will be weakened.

As described above, according to this embodiment, it is possible to reduce current overshoot and linking during current switching by using ν in the current switching circuit, which is effective in preventing malfunction of the circuit.

〔Effect of the invention〕

According to the present invention, it is possible to completely reduce the ringing of the sense output signal and the digit line clamp signal, and also to prevent the saturation of the transistor that switches the digit line clamp current, making it difficult for malfunctions to occur, which is effective in improving the performance of the circuit. be.

[Brief explanation of the drawing]

FIG. 1 shows a sense circuit with a conventional current switching circuit, FIG. 2 shows a sense circuit with a current switching circuit according to the present invention, and FIGS. 3, 4, and 5 provide a detailed explanation of the present invention. This is a route map. 'fJ+ 口SZ Figure VJ 3 Figure 4 Old Figure 5 Buddha Gin ℃1

Claims (1)

[Claims] 1. In a current switching circuit having a plurality of transistors whose current sources and emitters are connected to the current source and whose bases are connected to independent drive lines, the emitter of each transistor and the current supply A current switching circuit characterized by inserting a resistor between the wires. 2. A plurality of pairs of digit lines, a read transistor whose emitter is connected to each digit line and which performs current switching operation between the memory cell and the collector of the read transistor connected to one of the digit lines of each pair. a commonly connected first signal line; a common-base first transistor connected to the first signal line via a resistor;
a second signal line commonly connected to the collectors of the read transistors connected to the other of the digit lines of each pair; and a second transistor with a common base connected to the second signal line via a resistor. A current switching circuit with