JPH0321999B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a memory device such as a static MOS memory device.

[Conventional technology]

FIG. 1 shows an example of a conventional static type MOS memory device, and is a block diagram of its main parts.

In Figure 1, 1 and 2 are memory cell groups (memory planes), and their unit circuits (memory cells) 3
consists of four MOS transistors 4, 5, 6, and 7 (hereinafter abbreviated as MOST) and resistors 8 and 9. This memory cell is accessed by a decoder 12 that drives word lines 10 and 11, and an output signal appears as a minute potential difference on data lines 13 and 14.
Appears on common data lines 17 and 18 through MOSTs 15 and 16 for switches. Since the drains of all the switches MOST are connected to the common data lines 17 and 18, parasitic capacitance becomes large, which hinders high-speed operation of the memory device. For this reason, this common data line is usually divided into a plurality of lines using MOST in order to improve performance. 1st
In the figure, as an example, it is shown divided into two parts. The minute signal mentioned above is therefore 19,20
Alternatively, it is selected by turning on either MOST 21 or 22, and is supplied to input terminals 24 and 25 of sense amplifier 23. 26, 27 and 2
MOST of 8, 29, 30, 31 is data line 13,
14 and common data lines 17, 18, 32, 33
This is a load to maintain the voltage at a predetermined potential. In addition, 3
4 is an output buffer circuit.

In the memory device having the above configuration, the circuit shown in FIG. 2 has conventionally been used as the sense amplifier 23 and output buffer circuit 34 that amplify the minute signals on the common data lines 17, 18, 32, and 33.
In the figure, 24 and 25 are input terminals of the sense amplifier 23, and common data lines (17, 18, 3
2, 33) is input. 35, 36
37 and 38 are a pair of differentially connected N-type MOSTs (hereinafter abbreviated as NMOST) which receive a minute differential potential between input terminals 24 and 25, and 37 and 38 are P-type MOSTs (hereinafter abbreviated as NMOST).
(abbreviated as PMOST) serves as a load (load element). The gate and drain of PMOST 38 are commonly connected, and PMOST 37 and 38 operate as a constant current source. In other words, PMOST37 and 38 are
It operates as a load for the drains of NMOS35 and 36.

Now, V _cc − is applied to input terminals 24 and 25, respectively.
It is assumed that a potential of V _th , V _cc −V _th −ΔV is applied. However, V _cc : Power supply voltage, V _th : For example, in Figure 1
Threshold voltage of NMOST 36, ΔV: A minute potential difference (the same applies below) that occurs when a memory cell is accessed. Node 39 then goes to a high potential, reducing the current flowing through PMOST 37, causing node 40 (the output terminal of the sense amplifier) to
further lowers the potential of The NMOST 41 is a switch that is activated only when its gate terminal 42 is brought to a high potential by the activation control pulse signal. In this way, the output terminal 40 of the sense amplifier
A signal is outputted to, which signal is further amplified by inverter circuits 43 and 44 and transmitted to output buffer circuit 34.

The output buffer circuit 34 is the output transistor 4
5, 46, Logic section 4 controlled by signal/CS created by write signal and chip select signal
7, 48, and inverter circuits 49, 50, two signals are input: a signal 51 obtained from the output signal of the sense amplifier 23 via the inverter circuit 43, and a signal 52 obtained from the inverter circuit 44. Ru. Note that 53 is an output terminal of the output buffer circuit 34.

[Problem to be solved by the invention]

However, as a result of studies conducted by the present inventors, it has become clear that the conventional memory device equipped with the sense amplifier and output buffer circuit configured as described above has the following basic problems.

That is, in order to speed up the sense amplifier 23 itself in FIG.
It is necessary to use large-sized transistors for the PMOSTs 37 and 38, and to increase the current flowing through the switch MOST 41 in response to the control pulse signal supplied to the gate terminal 42, but this is not possible due to the integration density or power consumption of the integrated circuit. There is a problem.

Furthermore, as a result of studies conducted by the present inventors, it has become clear that the conventional memory device described above still has room for improvement in the following points. That is, since there is only one signal output line between the output of the sense amplifier 23 and the input of the inverter circuit 43 of the output buffer circuit 34 in the subsequent stage, this one signal output line is free from noise (for example, a switch).
Noise, etc. caused by the control pulse supplied to the gate terminal 42 of the MOST 41 is likely to be induced, and in response to this noise, the output buffer circuit 34
One of the output MOSTs 45 and 46 becomes conductive and a noise component is generated at the output terminal 53.

Since only one output line is output from the sense amplifier 23, it is necessary to generate two input signals 51 and 52 to the output buffer circuit 34 via an inverter circuit.

A delay inevitably occurs between the two input signals 51, 52, and in order to align the phases of the input signals 54, 55 to the output transistors 45, 46 and reduce the through current consumed in the output transistors 45, 46. , it is necessary to match the phases in the logic sections 47 and 48 and the inverter circuits 49 and 50, which complicates the circuit design.

Since it is necessary to match the phases of the input signals 54 and 55 of the output transistors, the overall delay time is inevitably determined by the signal 52 which is slower than the signal 51.

Therefore, an object of the present invention is to solve the above-mentioned problems and to speed up the sense amplifier itself of a memory device.

Further, according to the embodiments of the present invention, it is possible to provide a memory device that is less susceptible to noise and operates at high speed.

[Means to solve the problem]

In order to achieve the above object, in the memory device of the present invention, the amplifier circuit section of the sense amplifier is
A conventional amplifier circuit that receives minute differential potentials between two input terminals (portion surrounded by broken lines in Figure 2) 56
Two sets of amplifier circuits are used, and a capacitive element is connected between the output terminal and the input terminal of these two amplifier circuits.

Further, according to a specific embodiment of the present invention, two signal lines are arranged between the outputs of these two amplifier circuits and the input of the output buffer circuit in the subsequent stage,
The two output transistors of the subsequent output buffer are made to respond to two amplified signals of the same phase and opposite phase obtained on the main signal line.

[Effect]

Positive feedback of the signal occurs through the capacitive element connected between the output terminal and the input terminal of the two amplifier circuits, and the output signal of the output terminal in response to the signal of the input terminal is transferred to the input terminal via this capacitive element. positive feedback to accelerate the output signal at the output terminal.

Further, according to a specific embodiment of the present invention, when noise is induced in one of the two signal lines arranged between the output of the two amplifier circuits and the input of the subsequent stage, the noise is also induced in the other. Noise in phase with the noise is induced. However, although the subsequent output buffer circuit responds to the difference signal component between the two signal lines, it has a circuit configuration that is difficult to respond to the in-phase signal component of these two signal lines. It becomes possible to reduce noise components at the output terminal of the circuit.

Furthermore, two amplified signals of opposite phases for driving the inputs of the two output transistors 45 and 46 of the output buffer circuit 34 in the subsequent stage can be prepared without using the conventional inverter circuit 44 for logic inversion shown in FIG. , through-current is reduced, and high-speed memory operation is achieved.

〔Example〕

The present invention will be explained in detail below with reference to Examples.

FIG. 3 is a circuit diagram showing an example of the configuration of a sense amplifier and an output buffer circuit used in the memory device of the present invention.

In FIG. 3, the same reference numerals and symbols as those described above indicate the same or equivalent parts, and the explanation will be omitted as appropriate. Further, 35, 36 and 35', 36' are a pair of NMOSTs that receive minute differential potentials read from the memory cells, respectively.
37, 38 and 37', 38' are loads
It is PMOST. That is, two sets of portions 56 surrounded by broken lines in FIG. 2 are symmetrically connected.
Both PMOST38 and 38' have their gates and drains connected in common.
Since 8', 37, and 37' operate as constant current sources, high-speed switching can be performed.
In addition, NMOST 41 connected to the sources of PMOST 38, 38', 37, and 37' activates the sense amplifier only when a high level ("1") control pulse signal is supplied to its gate terminal 42. It's a switch. The sense amplifier having the above configuration has two output terminals 40 and 40', and the output signals from these terminals are sent to the inverter circuit 5 provided in parallel.
7, 58, amplified, and transmitted to the output buffer circuit 34.

When the voltage at the input terminal 24 of the sense amplifier becomes higher than the voltage at the input terminal 25, the MOST 35
Since the conductivity of MOST 35' increases and the conductivity of MOST 35' decreases, the sense amplifier output terminals 40,
40' change toward a low level and a high level, respectively. These output terminals 40, 40' are connected to inverter circuits 57, 5 via two signal lines L1, L2.
8, the outputs of the inverter circuits 57 and 58 change to high and low levels almost simultaneously.

Therefore, when the output control signal CS is at a high level, the outputs of the NAND gate circuits 47 and 48 change to a high level and a low level almost simultaneously, respectively.
The outputs 54 and 55 of the inverter circuits 49 and 50 also change to low level and high level, respectively, almost simultaneously. In this way, the output MOSTs 45 and 46 become non-conductive and conductive, respectively, almost simultaneously, and an output signal at approximately the ground level appears at the output terminal 53.

On the other hand, when the voltage relationship between the input terminals 24 and 25 of the sense amplifier is opposite to that described above, an output signal at approximately the level of the power supply voltage _Vcc appears at the output terminal 53, contrary to the above.

Next, FIG. 4 is a diagram showing an embodiment of the sense amplifier section of the present invention. In FIG. 4, the sense amplifier 23' shown in black box is the same as the sense amplifier 23' shown in FIG.
0.40'). Furthermore, in FIG. 4, the output terminal 40' and the input terminal 24
A capacitor 60 is connected between the output terminal 40 and the input terminal 25, and a capacitor 59 is connected between the output terminal 40 and the input terminal 25.

When the input terminals 24 and 25 of the sense amplifier 23' become high level and low level, respectively, the output terminal 4
0,40' changes to high level. Therefore, the high level output change at the output terminal 40' is caused by the capacitor 60.
Positive feedback is sent to the input terminal 24 via the output terminal 4.
A low level output change of 0 is positively fed back to the input terminal 25 via the capacitor 59, and output to the output terminals 40, 4.
The level change of 0' is accelerated.

FIG. 5 shows operating waveforms of the sense amplifier, where a is the input/output waveform diagram of the present invention and b is the conventional sense amplifier. In the figure, the dotted line is the input waveform from the common data line to the sense amplifier section, and the solid line is the output waveform of the sense amplifier. The delay time of the amplifier circuit itself of the present invention is about 2ns,
It can be seen that the output waveform is faster than the output waveform of the conventional circuit (Figure 2), and the input voltage amplitude of 0.3V is amplified to approximately 2.5V.

A and B in FIG. 5a are due to the coupling effect of the capacitors 59 and 60 shown in FIG. 4, and the output amplitude can be increased during switching, thereby increasing the operating speed of the next stage circuit.

In addition, in the embodiment shown in FIG.
Since the phases of the two amplified signals of opposite phases for driving the inputs of the two output transistors 45 and 46 of the output buffer circuit 34 in the subsequent stage are aligned without using the inverter circuit 44 for logic inversion shown in the figure, the through current can be reduced. At the same time, high-speed memory operation is realized.

In addition, in this example, NMOST35,
36, 35', 36' drain load
PMOST37, 38, 37', 38' are input terminals 2
Output terminals 40, 4 in response to the difference signals of 4, 25
0' is charged at high speed, while this input terminal 24, 25
NMOST35,36,3 in response to the difference signal of
Since outputs 5' and 36' are discharged at high speed, high-speed memory operation is realized.

Furthermore, in this embodiment, two signal lines L
1. Even if in-phase noise is induced in L2, the output of the output buffer circuit in the subsequent stage MOST45,46
The gates of are controlled in-phase in response to this noise,
Since the degree of conductivity changes similarly, the output terminal 53
It is possible to significantly reduce the noise components transmitted to the

Furthermore, in the monolithic integrated circuit constituting the circuit of the embodiment shown in FIG.
It has the advantage that it is easy to obtain a DC balance of 0'.

Furthermore, in the embodiment shown in FIG. 3, since the switching means consisting only of the MOST 41 is connected to the sources of the two differential pair connection NMOSTs 35, 36, 35', 36', the sources of the NMOSTs 35, 36 and Compared to the case where separate switching means are provided for the sources of NMOST 35' and 36', this method not only reduces the number of circuit elements but also has the advantage that it is easier to obtain DC balance between the two outputs 40 and 40'. .

The present invention is not limited to the above embodiments, and various modified embodiments can be adopted.

For example, in order to prevent an increase in delay time due to parasitic capacitance on the common data line, a method is used in which multiple sense amplifiers are used depending on the division of the common data line, and only one of them is activated to extract the output signal. In that case, the inverter circuits shown in FIG. 3, such as 57 and 58, may be replaced with selected logic sections.

〔Effect of the invention〕

As explained above, according to the present invention, since the change in the output signal of the sense amplifier is positively fed back to the input terminal, the change in the output signal of the sense amplifier is accelerated.
The sense amplifier itself of the memory device can be made faster.

According to the embodiment of the present invention, even if in-phase noise is induced in the two signal lines arranged between the outputs of the two amplifier circuits of the sense amplifier and the input of the subsequent circuit, Since the subsequent circuit has a circuit configuration that is less sensitive to the in-phase signal components of the two signal lines, it is possible to reduce the noise component at the output terminal of the subsequent circuit, and also to reduce the noise component at the output terminal of the subsequent circuit. Since the phases of the amplified signals of opposite phases for driving the two output transistors are aligned, through current is reduced and high-speed memory operation is realized.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram showing an example of a conventional memory device, FIG. 2 is a circuit diagram showing an example of the configuration of a conventional sense amplifier section and an output buffer circuit section, and FIG. 3 is a circuit diagram showing an example of the configuration of a conventional sense amplifier section and an output buffer circuit section. and a circuit diagram showing one embodiment of the configuration of the output buffer circuit section, FIG. 4 is a circuit diagram showing another embodiment of the sense amplifier section of the present invention,
FIG. 5 is an operational waveform diagram in the present invention and a conventional example. <Explanation of symbols>, 1, 2...Memory cell group (memory plane), 3...Unit circuit (memory cell),
12...decoder, 17, 18, 32, 33...
Common data line, 23, 23'... sense amplifier,
24, 25... sense amplifier input terminal, 34,
34...Output buffer circuit, 35, 36, 35',
36'...Element constituting a differential pair, 37,3
8, 37', 38'...load element, 40, 40'
...Sense amplifier output terminal, 56...Amplification circuit, 59, 60...Capacitor.

Claims (1)

[Claims] 1. In a memory device comprising a memory cell and a sense amplifier for amplifying a signal read from the memory cell, a signal applied between a first and a second input terminal. first and second amplified output signals responsive to the differential input signal and respectively generating at their output terminals an amplified output signal that is in phase with the signal at the first input terminal and in opposite phase with the signal at the second input terminal; The sense amplifier is configured by an amplifier circuit, and the first amplifier circuit of the first amplifier circuit
and the second input terminal of the second amplification circuit are commonly connected and connected to the output terminal of the first amplification circuit via a first capacitive element, The second input terminal of the circuit and the first input terminal of the second amplifier circuit are commonly connected, and the second input terminal of the circuit is connected to the output terminal of the second amplifier circuit via a second capacitive element. A memory device characterized by: 2 The sense amplifier configured by the first and second amplifier circuits includes first, second, third,
a fourth transistor; and fifth, sixth, seventh, and eighth transistors having conductivity types opposite to those of the first, second, third, and fourth transistors; The sources of the third and fourth transistors are connected to a first operating potential point, the sources of the fifth, sixth, seventh, and eighth transistors are connected to a second operating potential point, and the sources of the first transistor and the gate of the third transistor are connected, and the gate of the second transistor and the gate of the fourth transistor are connected, and a voltage responsive to a current at the drain of the second transistor is formed. is generated between the source and drain of the sixth transistor, and the voltage generated between the source and drain of the sixth transistor is applied between the source and gate of the fifth transistor. A current flowing through the drain of the transistor No. 5 is set, and a voltage responsive to the current at the drain of the third transistor is generated between the source and drain of the seventh transistor. By applying the generated voltage between the source and gate of the eighth transistor, a current flowing to the drain of the eighth transistor is set, and the current flowing to the drain of the first transistor and the current flowing to the drain of the first transistor are set. A first amplified signal is obtained by the difference current between the current flowing in the drain of the fourth transistor and the current flowing in the drain of the eighth transistor, and the first amplified signal is obtained by the difference current between the current flowing in the drain of the fourth transistor and the current flowing in the drain of the eighth transistor. The sense amplifier is configured to obtain a second amplified signal, and the first amplified signal and the second amplified signal of the sense amplifier are connected to a first input of a subsequent circuit via a first signal line and a second signal line, respectively. Claim 1 characterized in that the second input is transmitted to the second input.
Memory device as described in section. 3 The sense amplifier configured by the first and second amplifier circuits includes first, second, third,
a fourth transistor; and fifth, sixth, seventh, and eighth transistors having conductivity types opposite to those of the first, second, third, and fourth transistors; The sources of the third and fourth transistors are connected to a first operating potential point, the sources of the fifth, sixth, seventh, and eighth transistors are connected to a second operating potential point, and the sources of the first transistor and the gate of the third transistor are connected, and the gate of the second transistor and the gate of the fourth transistor are connected, and the transistor responds to the current at the drain of the second transistor. A voltage is generated between the source and drain of the sixth transistor, and the voltage generated between the source and drain of the sixth transistor is applied between the source and gate of the fifth transistor. A current flowing through the drain of the fifth transistor is set, and a voltage responsive to the current at the drain of the third transistor is generated between the source and drain of the seventh transistor. By applying the voltage generated between the source and gate of the eighth transistor, a current flowing to the drain of the eighth transistor is set, and the current flowing to the drain of the first transistor and the above are set. A first amplified signal is obtained by the difference current between the current flowing through the drain of the fifth transistor, and the difference current between the current flowing through the drain of the fourth transistor and the current flowing through the drain of the eighth transistor. the sense amplifier is configured to obtain a second amplified signal, and the first amplified signal and the second amplified signal of the sense amplifier are connected to a first input of a subsequent circuit via a first signal line and a second signal line, respectively. and a second input, and the subsequent circuit has ninth and tenth circuits connected in series between the first operating potential point and the second operating potential point.
the number of logic circuits connected between the first input of the subsequent circuit and the control input of the ninth transistor, and the number of logic circuits connected between the second input of the subsequent circuit and the tenth transistor. By setting the number of logic circuits connected between the control inputs of the transistors to be equal, the control inputs of the ninth and tenth transistors are provided with mutually opposite complementary signals having substantially no phase difference. 2. The memo device according to claim 1, wherein the memo device is driven. 4. The memory according to claim 2 or 3, wherein the gate and drain of the sixth transistor are connected, and the gate and drain of the seventh transistor are connected. Device. 5. A patent characterized in that switch means controlled by a control signal is connected between the sources of the first, second, third, and fourth transistors and the first operating potential point. A memory device according to claim 4. 6. The switching means is constituted by other transistors, and the operating currents flowing through the first to eighth transistors are substantially set only by the currents flowing through the other transistors. A memory device according to claim 5. 7. The subsequent circuit has high sensitivity to the difference signal component between the first input and the second input, and has low sensitivity to the in-phase signal component between the first input and the second input. A memory device according to any one of claims 1 to 6, characterized in that: 8. The memory device according to claim 7, wherein the subsequent circuit is an output buffer circuit. 9 A signal read from the memory cell via a common data line transmitting a read signal from the accessed memory cell is transmitted to the gates of the first and third transistors of the sense amplifier and the second and fourth transistors of the sense amplifier. Claims 1 to 8 are characterized in that the signal is transmitted to the gate of the transistor.
The memory device according to any of paragraphs.