KR950003138B1 - Device for determining circuit character - Google Patents

Abstract

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Description

Device for predetermining circuit characteristics

1 is a schematic diagram of a preferred embodiment of the present invention.

2 is a schematic diagram of another preferred embodiment of the present invention using a feedback circuit to improve accuracy and stability.

3 is a schematic representation of the embodiment of FIG.

4 is a schematic representation of the embodiment of FIG.

* Explanation of symbols for main parts of the drawings

12, 100: input terminal 14: reference voltage network

16,34,36,38,40,42,44,140,142,144,146 resistors

18: Zener Diode 20, 102: Comparator

22, 24, 126, 128: switch 26, 120: inverter

28, 138: voltage follower amplifier 30, 139: output terminal

32: voltage divider 46: wire

104,108,114,116,124,136: P-channel device

106,110,118,122,130,134: N-channel device

112: constant current source

The present invention relates to a circuit capable of executing both internally preselected characteristics in an electronic circuit and externally user selectable characteristics. More specifically, the present invention relates to a circuit that selects between a predetermined characteristic embedded in a circuit and a user defined characteristic that can be selected by the user and transmitted to the circuit by an indication on an input terminal.

The present invention can produce a circuit having a fixed characteristic, for example a reference voltage of + 5V DC, and the output may be arbitrarily set by the user to any other voltage between supply voltage levels such as 1.3V. To be. In addition, this circuit essentially uses an auxiliary input terminal, which is typically required to achieve this function by essentially detecting the application form and changing the internal circuit form to produce the desired level of output by using a single input terminal. Eliminate the need

Recently manufactured circuits have fixed or user definable characteristics. In addition, some circuits may select predetermined or user-defined characteristics. This gives the circuit more flexibility because it can be used in applications that require the same fixed or user definable characteristics.

Electrical circuits operate on electrical quantities such as voltage, current, frequency, and charge. The magnitude of these quantities is important because they can, for example, set circuit parameters or be used to display information. In digital circuits, high level voltages can be used to represent true logic values, and low level voltages can be used to represent "false" logic values. Unlike the two levels generated in the binary digital circuit, the analog circuit can use an infinitely variable voltage level number between the two thresholds to proportionally represent the small or small amount of the characteristic or parameter.

There is also a need to provide a circuit capable of determining a reference level for the amount of electricity. Some of these reference levels are sometimes used to be an industry standard. For example, + 5V DC is the voltage level typically used for powering in most digital circuits. Similarly, +15 and -15V DC are typically used for analog circuit power supply voltage levels. Another common group of circuits for generating voltage levels is the voltage reference circuit. Common voltage reference circuit outputs are + 2.5V, 5V, and 10V. For many other applications, a non-common voltage level such as 1.3V may be needed when the circuit is operating on a 1,5V battery.

Typically, manufacturers supply dedicated circuits with characteristics that include a common (or standard) level. In the case of solidification which is not common, different classes of circuits are generally provided which are not dedicated and have a user selectable characteristic. For example, voltage reference circuits are provided as dedicated + 5V or 10V reference circuits, or as non-dedicated reference circuits that can be set to a specific voltage level, for example by using a simple resistive voltage divider.

Circuits that combine several properties are also known. Such circuits typically have an input for selecting between a predetermined characteristic and a user selectable characteristic to adjust the amount selectable by the user. Typically, two input terminals are needed to achieve this function in the circuit. First, a digital input terminal is needed to determine the type of application (ie, whether the circuit uses predetermined or user defined characteristics). Second, the analog input terminal is used as a means for providing a user defined characteristic.

As circuitry and functionality become more complex, it is desirable to reduce the number of input and output terminals without losing functionality. Therefore, it is desirable to combine as many functions as possible on the circuit without overusing the input or output terminals.

Described herein is a circuit that selects between preselected circuit characteristics and a user selectable characteristic and allows the user to specify a user selectable characteristic through a single input terminal.

In a preferred embodiment, the characteristic is a DC voltage, which can be converted to current, frequency or the like by known means. The DC input voltage present at the single input terminal is sensed and compared with the negative DC supply voltage in the comparator circuit.

If the DC input voltage is equal to the negative DC supply voltage, the switching network connects the internally set reference voltage to a voltage follower or source follower amplifier. If the DC input voltage is greater than the negative DC supply voltage, the switch network connects the DC input voltage at the single input follower terminal to the source follower amplifier.

The output of the source follower circuit can be used at the output terminal or can be connected to a device such as a voltage-to-current converter or a voltage-frequency converter to supply circuit parameters other than voltage to the output terminal.

In a preferred embodiment, the entire circuit can be fabricated on a single semiconductor substrate using CMOS technology.

It is an object of the present invention to provide a circuit capable of selecting between a user selectable characteristic and a predetermined characteristic.

Another object of the present invention is to provide a circuit which can select between predetermined characteristics and user selectable characteristics by using one single input terminal.

It is a further object of the present invention to provide such a circuit which is more convenient to use.

It is a further object of the present invention to provide such a circuit which is easier to assemble into more electronic circuits.

Now, other objects and advantages of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a simplified schematic diagram of the circuit of the present invention is shown.

The circuit 10 selects between a predetermined characteristic provided at one input terminal 12 and a user selectable characteristic. In the following description, the characteristic will only be referred to as DC constant voltage as an example. Nevertheless, those skilled in the art will appreciate that the present invention includes other circuit parameters and characteristics such as current, frequency, and the like. Those skilled in the art can readily see how this DC voltage can be converted to current, frequency or other common parameters and characteristics that appear within the electronic circuit.

The circuit 10 is generated by a user selectable voltage that can be placed on the input terminal 12 and by a reference voltage source such as, for example, a network 14 consisting of a resistor 16 and a zener diode 18. It is possible to select between the internally preset voltages.

The circuit 10 operates by comparing the voltage at the input terminal 12 in the comparator 20 with the negative DC supply voltage V- supplied to the circuit. If the voltage at the input terminal 12, i.e., the comparator 20 input, is equal to the negative supply voltage (shown by the dashed line 21), then the output of the comparator 20 opens the switch 22, The switch 24 is closed via the inverter 26. When the switch 22 is open and the switch 24 is closed, the output of the internal voltage network 14 is connected to the input of the voltage follower amplifier 28.

However, if the voltage at the input terminal 12 is greater than the negative supply voltage (shown by the dashed line 29), the output of the comparator 20 closes the switch 22 and switches the switch 24 to the inverter ( Through 26). In this case, the user supply voltage appearing at the input terminal 12 is connected to the input of the voltage follower amplifier 28.

The output of the voltage buffer amplifier 28 can be connected to the output terminal 30 as shown, or can be used to drive commonly used circuits such as voltage-frequency converters or voltage-current converters.

In the embodiment of the invention shown in FIG. 1, the voltage supplied to the input terminal 12 is positive and negative DC through a voltage divider 32 consisting of resistors 34 and 36, for example. It can be a voltage derived from the supply voltage.

Those skilled in the art can readily appreciate that several feedback means can be used to further increase precision. This embodiment is shown in FIG.

As in the circuit of FIG. 1, the comparator 20 of FIG. 2 compares the voltage at the input terminal 12 with a negative supply voltage. The outputs of comparator 20 and inverter 26 drive switches 22 and 24 to select a predetermined voltage or a user supplied voltage in the manner described with reference to FIG. However, in the embodiment of FIG. 2, the amplifier 28 is connected in a feedback configuration.

The output of the reference voltage network 14 is supplied to the non-inverting input of the amplifier 28. If the input terminal 12 is at a negative supply voltage [shown by the dashed line 48], the output of the amplifier 28 is via an internal resistor network consisting of a switch 24 and resistors 38 and 40. Return to the inverting input of the amplifier 28.

As is well known, the gain of amplifier 28 is determined by the values of resistors 38 and 40. However, if the output terminal 30 has resistors 42 and 44 connected to this output terminal, and the input terminal 12 is connected as shown by the dotted line 46, the output of the amplifier 28 is a resistor. Return to the inverting input is via a feedback loop consisting of 42 and 44, line 46 and switch 22.

Referring to FIG. 3, which is a schematic diagram of the embodiment of FIG. 1, input terminal 100 is connected to comparator circuit 102. Comparator circuit 102 is composed of P-channel device 104, N-channel device 106, P-channel device 108, and N-channel device 110. N-channel devices 106 and 110 are matched pairs, and P-channel devices 104 and 108 are also nearly matched pairs. That is, the size of P-channel device 104 is slightly larger than P-channel device 108.

The comparator 102 is supplied with current by a constant current source 112 consisting of P-channel devices 114 and 116 and N-channel device 118. The amount of current supplied by the constant current source 112 is determined by the voltage on the gate of the N-channel device 118 in relation to the negative DC supply voltage. The reference voltage source 14 of FIG. 1 functions satisfactorily as this reference voltage source.

Comparator 102 functions as follows. The constant current source 112 supplies all the constant current to the devices 104 and 106 on one side of the comparator 102 and the devices 108 and 110 on the other side. Both currents are equal when the gates of the P-channel device 104 connected to the input terminal 100 are at the negative supply voltage when these devices are matched. However, because the size of the device 104 is slightly larger than the device 108, some imbalance occurs, causing more current to flow through the devices 104 and 106 than the devices 108 and 110. Therefore, the voltage of the common connection of the P-channel device 108 and the N-channel device 110 tends to be lower than the voltage of the common connection between the P-channel device 104 and the N-channel device 106. .

Therefore, the output of the comparator, which is a common junction between the N-channel device 110 and the P-channel device 108, is at a low level, so that the input of the inverter 120 is at a low level, and the output is at a high level.

However, the voltage at terminal 100, i.e., the voltage at the gate of P-channel device 104 rises above the negative supply voltage, and P-channel device 104 is turned off. This causes the voltage at the common connection gates of the N-channel devices 106 and 110 to be turned towards the negative DC supply voltage so that the devices are turned off. Therefore, the voltage at the output of the comparator rises and provides a high level to the input of the inverter 120, thereby bringing its output to a low level.

Inverter 120 connected to the output of comparator 102 consists of an N-channel device 122 and a P-channel device 124 connected in series, the gates of which are connected together. When the input voltage to the gate becomes low and becomes near or equal to the negative supply voltage, the N-channel device 122 is turned off and the P-channel device 124 is turned on. Therefore, the output of inverter 120, which is a common source / drain connection of devices 122 and 124, is at a high level. If the input is at a high level, the N-channel device 122 is turned on and the P-channel device 124 is turned off, so the output is at a low level.

Switches 126 and 128 are composed of N-channel device 130 and P-channel device 132 and N-channel device 134 and P-channel device 136, respectively. Gates of P-channel device 132 and N-channel device 134 are connected to the output of inverter 120. Gates of N-channel device 130 and P-channel device 136 are connected to a common connection between the output of comparator 102 and the input of inverter 120.

In the first case, a negative supply voltage is present at terminal 100 (to select a predetermined characteristic) to bring the input of inverter 120 to a low level and to the output to a high level. The N-channel device 130 and the P-channel device 132 connected to the output of the inverter are turned on, and the N-channel device 134 connected to the output of the inverter and the P-channel device connected to the input of the inverter 136 is turned off. Switch 126 is closed and switch 128 is open.

For similar reasons, if the input of inverter 120 is high level and the output is low level, switch 128 is closed and switch 126 is open.

Depending on which of the switches 126 and 128 is closed, the reference voltage Vref at the input terminal 100 or a user supplied voltage is supplied to the amplifier 138 configured as a source follower amplifier. The output of the amplifier 138 is connected to the output terminal 139 and exhibits an output voltage almost equal to the reference voltage Vref or the voltage supplied by the user on the input terminal 100.

Referring to FIG. 4, those skilled in the art can see that the illustrated embodiment is the same in best respect as the embodiment of FIG. The connections between the switches 126 and 128 and the inverter amplifier and output terminals are different, thus reflecting the use of feedback.

In the embodiment of Figure 4, the principle of feedback is used to help stabilize and control the accuracy of the output. In this embodiment, a selection is made between an internal feedback loop consisting of resistor 140 and resistor 142 and a user selectable external feedback loop consisting of resistors 144 and 146.

In the embodiment of FIG. 4, the non-inverting input of the amplifier 138 is connected to a reference voltage supplied by the zener diode resistor network 14 of FIGS. 1 and 2, for example. The internal feedback loop consists of resistors 140 and 142, their common junctions being connected to a switch 128. The outer feedback loop consists of resistors 144 and 146, whose common junction is connected to switch 126 via input terminal 100.

In the embodiment of FIG. 4, when the input terminal 100 is connected to the negative DC supply voltage as shown by the dotted line 148, the switch 128 is closed and the switch 126 is open. Therefore, the internal feedback loop through the amplifier 138 is enabled, and the voltage appearing at the output terminal 139 is determined by the ratio of the values of the resistors 140 and 142 to the value of the reference voltage Vref.

However, when the input terminal 100 is connected to the junction of the resistors 144 and 146 as shown by the dashed line 150, the switch 126 is closed and the switch 128 is opened to the outside through the amplifier 138. The feedback loop is set. Therefore, the voltage at the output terminal 139 is determined by the ratio of the value of the resistors 144 and 146 to the value of the reference voltage Vref.

Those skilled in the art will appreciate that the preferred CMOS embodiments described herein use N-channel and P-channel enhancement devices, but others such as depletion or bifla type transistors. It will be appreciated that devices can be used. Also, those skilled in the art will not connect the substrates of all N-channel devices to the negative DC supply voltage and the substrates of the P-channel devices to positive DC supply, although not shown in FIGS. 3 and 4. It can also be seen that the voltage is connected.

Claims (1)

An integrated circuit for selecting between internally predetermined parameters and externally supplied user selectable parameters, the input terminal and gate being connected to the input terminal and the drain being connected to the first node. A first comparator P-channel transistor, a source connected to a first voltage source, a drain and a gate connected to a source of the first comparator P-channel transistor, a drain to a first comparator, a drain connected to the first node, A second comparator P-channel transistor connected to said first voltage source, a drain connected to a source of said second comparator P-channel transistor, a gate connected to a gate of said first comparator N-channel transistor, and a source connected to said first voltage source A second comparator P-channel transistor connected, the output of the comparator being the second comparator A connection between a source of a null transistor and a drain of the second comparator N-channel transistor, the output of the comparator taking a first state if the voltage on the input terminal is less than or equal to the first voltage, and the input terminal A comparator taking a second state if the phase voltage exceeds the first voltage, a constant current source connected to the first node, an inverter having an input and an output connected to the output of the comparator, and an output connected to the input and output terminals. A control means for operating a first switch when the comparator is in the second state, the voltage follower having a voltage follower amplifier, connected between the input terminal and the input of the voltage follower amplifier, and in response to an output of the comparator A first switch comprising: and an output of the comparator connected between the input internal reference voltage source of the voltage follower amplifier; In response, a second switch unit for setting the circuit characteristics, characterized in that it comprises a pre-containing control means for the comparator operates the second switch when in the first state.

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