Technical Field :

Electronics

Previous Method:

In order to convert an analog signal to a digital signal, IC's like ADC0804, MC14433 and others are currently being put to use.

Principles of Operation:

There are numerous techniques used by current IC's to convert from analog to digital; each has its advantages and disadvantages. Speed and accuracy are the main factors that determine their efficiency.

The three main techniques are:

1. Successive approximation

2. Integration (single, double, quadratic)

3. Parallel comparator

The first technique, being the most commonly used in PIC Microcontrollers and most other processors, will be illustrated.

Successive Approximation Method:

A guess (prediction) is made for the first input, which gets converted to analog and then compared to the actual value of the input. The result will determine whether the value of the next estimation (guess) will be increased or decreased.

And the following panel shows an example of the successive approximation technique - see panel (1).

The conversion process starts upon applying a start pulse to the start/stop pin, changing the value of the Most Significant Bit of the control register to a high state.

^■ Assuming an 8-bit register, its initial guess value will become 1000,0000, which is ½ V _ref half the reference voltage. Then that value gets converted to analog using a DAC, and compared to the analog input using a comparator. If the input is greater than the previously guessed value, the comparator gives an output of a high state causing the register to retain its MSB high state, and the converter continues to give an output of ½ V .

^■ The converter now proceeds to the next bit, giving it a high state. Thus giving the register the binary value of 1100 0000 . ^■ This means the value of the ADC has been increased by ¾ V , to become ( ½ + ¾ )V . Then, this voltage will be compared to the analog input. If its value is greater than that of the input, this bit (MSB-1) will be changed back to zero.

■

^■ SEE panel (1)

^■ Then bit (MSB-2) will be set to high "1", giving the register the value of 1010 0000 . This will increase the ADC output by 1/16 V after it's been decreased by ½ V . Thus the ADC approximation becomes ( ½ + 1/16)V. And so on ...

^■ In other words, as long as the analog input is greater than its approximation, the current bit will be set to high "1". But if it's less than the approximation, the bit will be reset to "0" and the next condition is checked.

^■ The following panel shows the flow chart sketch of the algorithm of a successive method based ADC, which can be made into a program to get an ADC software.

■

^■ SEE panel (2)

Previous Method Insufficiency:

Most outstanding flaws of the previous method:

1. The relatively high cost of the currently used IC's, which is due to the numerous elements inside the IC, which contains a comparator, a clock, registers and other elements which are used to realize the previously mentioned algorithm.

SEE panel (3), components of the IC : ADC0804

2. High power consumption, due to huge number of inner components.

3. Low speed. This circuit takes a considerably large period of time to perform the numerous comparisons necessary to calculate the converted value.

4. Large area. When used as a module inside a larger chip, like a PIC, it demands a high chip/ board area, which affects the size of the PIC.

5. The accuracy of this kind of converters directly depends on the number of registers that store the converted values. Thus, an increase in its accuracy demands extra registers, which will increase its production cost. What's new about this invention?

It's the idea that analog values can be directly dealt with and treated like a digital signal using only one junction "diode", by employing the depletion region property. This can be done after introducing some modifications to the junction.

Those modifications, shown in the panel, are:

1. A number of contacts on both top and bottom sides of the junction, which will allow the current to flow through it, via its electrons and holes.

2. A layer of insulator on both sides of the junction, to stop the input current, limiting the input's effect to the electric field due to the voltage difference applied to the input.

(see the sketch of the electronic element after modifications) SEE panel (4)

This way, the flaws of the previous method are avoided:

1. The price of the component that will convert an analog signal to a digital signal (this invention), will cost about the same price of a single diode, which is an enormous reduction from the price of the previous part, which consisted of hundreds of transistors and logic gates. So, it will reduce the cost of producing an ADC by the cost of all hundreds of other elements that were eliminated.

2. This component will not consume large amounts of power because.

a. It's only a single element.

b. Doesn't need a large algorithm to convert an analog input to a digital output.

3. It will be faster, because it can directly convert an analog input to digital, unlike the IC that needs an algorithm and a series of comparisons to do it.

4. Does not demand a large area on the chip, and it's about the size of a single diode.

5. Its conversion accuracy depends on the number of contacts introduced to the junction, which will not demand a high cost. We only need to calibrate the distances between the contacts and determining their corresponding analog values. Detailed description:

There is a phenomena that happens within a diode called the depletion region, which is formed whenever an N-type crystal, like a Phosphor doped Silicon, comes to contact with a P-type crystal, like a Boron doped silicon.

See the sketch.

SEE panel (5-A)

The depletion region is basically an electric insulator, and it's directly affected by the voltage applied to its sides.

In case of a reverse connection, depletion region expands, as shown in the sketch.

SEE panel (5-B)

The width of the depletion region is proportional to the reverse voltage applied on it.

Taking advantage of this property, a set of contacts, e.g. A,B,C,D,E,F , can be connected, as in sketch, in a manner so that they will be short circuited together whenever the depletion region is narrow (when they're not in the range of the depletion region). And by applying increasing voltage, the depletion region increases due to the input's electric field, thus disconnecting the output, like a switch.

In case the circuit in the following sketch (panel 6) was subjected to a certain reverse biased input (in order to achieve input-depletion proportionality), contacts A,B,E,F become open circuit, while contacts C,D are short circuited with the input.

By determining the distance between these contacts and calibrating them, the input level can be read, whether it was voltage, temperature or something else, through its proportionality with the width of the depletion region .

SEE panel (6)

After applying input, depletion region increased, all connectors but C,D went open circuit .

Usage of the method:

This component may have a lot of applications, including but not limited to: Nano technology, since it's very small, very low power consumption.

It can be used to replace integrated circuits that convert from analog to digital. And can also be used inside PIC micro controllers to decrease its area and power consumption.

It can also be used along with sensors, like light sensors and heat sensors, which will be connected to its input, in order to switch on certain machines or sets at a certain temperature or light intensity, as the input will control which if the connectors will be on and off.

It can be used with a processor to control a certain module using variable analog voltage. E.g. at 3V, connect interface A to output, and at 4V, connect interface B to output.

It will be useful in the combinational logic field. Logical components will be developed to accept more input possibilities. There used to be only two possible inputs [0, 1]. But now, new circuits can be designed to accept more than to possible input, according to the number of output contacts. A three output contact component can accept [0, 1, 2].

It can also contribute to information storage. Information used to be stored as [0, 1] only. Using this component, more than one piece of information can be stored on the same unit. For example, if this component stores "6", this means the info stored id "110". It's noticeable that a lot of info can be stored on smaller units. It will cause a breakthrough in the memory industry.