Differential Instrumentation Amplifier with a Bridge Transducer Circuit

Posted by Micro System

on Tuesday, September 14, 2010

This is a circuit for differential instrumentation amplifier that has a resistive transducer (Rt).  A resistive transducer is a device whose resistance changes when a certain physical energy applied to it changes. Common examples include transducers with resistances that vary with temperature, pressure, and light shining on it. This is the figure of the circuit;

As in most bridge circuits, the components in this circuit's bridge network (consisting of Ra, Rb, Rc, and Rt) are chosen so that the bridge is balanced at a certain reference condition, i.e., Rc/Rb = Rt/Ra.  One way to do this is to make Ra=Rb=Rc=Rt=R at the chosen reference point. 
  
When the bridge above is balanced, Va = Vb, causing the input voltages to A3 to be equal and the output of A3 to be zero.  When the resistance of Rt changes, however, the bridge becomes unbalanced, causing a non-zero voltage Vab to appear across the inputs of A3. This, in turn, results in an output voltage Vo that is proportional to the change in resistance of Rt, i.e., Vo = (RF/R1)(ΔR/4R) Vdc where ΔR is the change in Rt's resistance.

IL300XC Isolation Amplifier Circuit for TMP01 Temperature Sensor

Posted by Micro System

on Sunday, September 5, 2010

This is a circuit for about IL300XC Isolation Amplifier circuit for TMP01 Temperature Sensor. This circuit is used in an environment that needs to be electrically isolated from the central processing area. This circuit uses an 8-pin opto isolator (IL300XC). IL300XC was chosen because it can operate across a 5,000V. To drive the LED connected between Pin 2 and Pin 1, this circuit uses an OP290 single-supply amplifier. the photodiode connected from Pin 3 to Pin 4 gives the feedback. This is the figure of the circuit;

 

The OP290 drives the LED, that there is enough current generated in the photodiode to exactly equal the current derived from the VPTAT voltage across the 470 kO resistor. On the receiving end, the current from the second photodiode is converted to a voltage through its feedback resistor R2. TO buffer the 2.5 V reference voltage of the TMP01, this circuit uses the other amplifier in the dual OP290. It will give the an accurate, low drift LED bias level without affecting the programmed hysteresis current. The bias level accuracy at receiving end is provided by A REF43.

The current of the photodiode is determined by following equation:
I1=(2.5V-VPTAT)/470K
The output voltage is determined by following equation:
Vout=2.5V-I2*R2
=2.5V-0.7*((2,5V-VPTAT)/470)*644K=VPTATT

R2 must be larger than R1 to achieve overall unity gain because the gain of IL300XC is less than 1.0. To correct for the initial gain accuracy of the IL300XC, A trim is used in this circuit. Just adjust the trim to get output voltage equal to VPTAT at any particular temperature. Both the OP90 and REF43 contribute no significant error because of drift and operate from a single supply.

Digitally Controlled Dual Polarity Amplifier Circuit

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This is a circuit for a Digitally Controlled Dual Polarity Amplifier circuit. The circuit (a) can give a means of amplifying a signal either in non inverting and inverting mode. When S2 is off and S1 is on, the non-inverting input of the op amp is fed by the signal. The circuit behaves as a regular inverting amplifier, When switch  S2 is on and S1 is off. A digital signal can be used to control the circuit if S1 and S2 are monolithic analog switches. This is the figure of the circuit;

A potentiometer can be used to replace the switches as shown in circuit (b). When the wiper is at the high end of the pot, the non-inverting mode is chosen and the inverting mode will be selected when it’s at the other end. Circuit (b) uses DS1267 linear  digital potentiometer. This circuit not only gives digital control of the polarity but also the amplifier gain. To accomplish the signal processing task, an “extra” pot in a circuit to be used because the digital potentiometers come in dual configurations. The DS1267 has the 3-wire interface, they are active-low CLK, RST and DQ. A wiper value of 11111111 will set the wiper to the high end of the pot, so the circuit is in a non-inverting configuration with gain = +1. an inverting configuration with gain = -1 is chosen when wiper value is 00000000 that set the wiper to the low end of the pot.

20dB VHF Amplifier Circuit

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This is a circuit for amplifier that can be used for VHF only. The amplifier is a circuit of high frequency RF with distinguishable materials. The amplifier as circuit strengthens the tendency of signal with concrete aid, depending on the frequency of signal. This is the figure of the circuit;

In this circuits are not included in joint action circuits. With that way is covered a wide spectrum of frequencies, without is differentiated abruptly the aid as for the frequency. With this provision we have smaller gain but big breadth of frequencies. The two rungs are same, with the same prices of materials and each rung offer aid roughly 10dB. The transistors and the remainder materials, because the industrial manufacture, have almost the same characteristics. Associates the particular characteristics of demagogues are altered mainly the aid of rung.

Each rung uses a transistor of type npn in provision of common emitter that functions in order A. his rungs works in provision of common emitter with null resistance in emitter. In each rung a network of resistances between the collectors and the bases polarize the transistors and ensures the operation of circuit. The junction between the rungs becomes via ceramic capacitors of small capacity from 0,1nF until 0,22nF (at preference ceramic). In the place of two rungs we can try various transistors of independent company or even different between them. The circuit of course cannot work with all of them. The tendency of catering should emanate from stabilised power supply with tendency 12V. Depending on the tendency of catering and the type of transistor, in each rung of amplifier it needs enter also different resistances.

FM Band Preamp Circuit

Posted by Micro System

on Thursday, August 5, 2010

This is a circuit for a high performance RF amplifier for the FM band which can be successfully built without any special test equipment. The output transformer is designed to resonate with the FET's drain capacitance at about 92 MHz giving the amplifier the highest gain at the low end of the band where the weaker stations operate. This is the figure of the circuit;


The performance of the amplifier is quite good. The noise figure is below 2 dB and the gain is over 12dB. The low noise figure and good gain will help car radios or home stereo receivers pick up those weak distant stations or the lower power "talk radio" and university stations. FM receivers loose signals abruptly so if your favorite station fades in and out as you drive, this amplifier can have a dramatic effect.

The coil is wound on a section of an ordinary pen cap. Find a ball-point or felt-tipped pen with a plastic cap with an outside diameter of 0.4 inches. Cut off a piece 0.6 inches long. Poke small holes 0.1 inches from each end to secure the ends of the primary winding. Wind a ten turn primary of solid copper telephone wire around the tube passing each end through the small hole to secure the winding. Any small-gauge insulated wire which nearly covers the tube will work but the common telephone cables (which typically contain 25 colorful twisted pairs) yield excellent prototyping wire. The secondary is two turns wound around the ten turns.

40W Audio Amplifier Using TDA2030

Posted by Micro System

on Friday, July 30, 2010

This is a design circuit for power amplifier that is very excellent 40W power amplifier design using TDA2030 IC and two transistors. This is the figure of the circuit;


The circuit employs only few components and does not require a dual power supply. The input signal is coupled to the non inverting input of TDA2030 through the DC decoupling capacitor C5. The TDA 2030 performs the major part of voltage amplification. As the IC performs amplification, the power supply current to the IC varies according to the input signal. The variations in the positive supply pin are coupled to the base of Q1 and variations in the negative supply pin are coupled to the base of Q2.The major part of current amplification is done by these two complementary transistors.

Speech Amplifier Circuit Using TDA7052

Posted by Micro System

on Tuesday, July 27, 2010

This circuit is a power amplifier that can be housed in the box containing the speaker to form a handy microphone amplifier. The device can be used by teachers, guides, lecturers etc for speaking in a crowdy or noisy environment. This is the figure of the circuit;


The circuit is designed base on the audio power amplifier IC TDA 7052.The IC can deliver a maximum power output of 1.2 W at a 6V supply. The audio signal from the microphone is pre amplified by the amplifier based on Q1 (BC 547) and give to the input of IC1 (pin 2).The POTR5 acts as a volume control. The capacitor C3 is used to bye pass the upper frequencies in order to avoid the Larsen’s effect(the microphone picking up speaker output to cause howls).

Multi Stage Amplifier Circuit

Posted by Micro System

on Monday, July 26, 2010

This is a circuit for multistage amplifier. By connecting three common-emitter amplifier circuit together the collector terminal of the previous transistor to the base (resistor) of the next transistor the voltage gains of each stage compound to give a very high overall voltage gain. This is the figure schematic of the circuit;


In this circuit was recommend building this circuit without the 1 MΩ feedback resistor to begin with, to see for yourself just how high the unrestricted voltage gain is. You may find it impossible to adjust the potentiometer for a stable output voltage (that isn't saturated at full supply voltage or zero), the gain being so high. Connect the 1 MΩ feedback resistor into the circuit, coupling the collector of the last transistor to the base of the first. Since the overall response of this three-stage amplifier is inverting, the feedback signal provided through the 1 MΩ resistor from the output of the last transistor to the input of the first should be negative in nature. As such, it will act to stabilize the amplifier's response and minimize the voltage gain. You should notice the reduction in gain immediately by the decreased sensitivity of the output signal on input signal changes (changes in potentiometer position). Simply put, the amplifier isn't nearly as "touchy" as it was without the feedback resistor in place.

The Simple Basic Op Amp Inverter Circuit

Posted by Micro System

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An operational amplifier is actually a high-gain differential amplifier, and as such has both an inverting and a non-inverting input. Both inputs must be connected in order for the circuit to work. This is the figure of the circuit;


The input and feedback connections are both made to the inverting (-) input. The non-inverting input (+) is grounded through a resistor. This is what forces the inverting input to be a virtual ground: the amplifier output voltage depends on the voltage difference between the two inputs, rather than the absolute voltage at either input. Because the input transistors inside the op amp do actually require a very slight input current, there is a very slight corresponding voltage drop across the resistors connected to those inputs. However, if the resistor connected to the non-inverting input is approximately the same as the parallel combination of R_in and R_f, the resulting voltage drops will be the same and will tend to cancel each other out. If R_in and R_f are each 10K, then a standard 4.7K resistor to the non-inverting input will be satisfactory in this capacity. We could also use a 5.1K resistor here.

Because the ratio of R_f/R_in completely controls the effective gain of the amplifier, these resistors should be as precise as possible. Radio Shack sells a package of 50 ¼-watt metal film resistors, having a tolerance of 1%. You don't have to use them in these experiments, but your results will be more accurate if you do. All results discussed in these pages will be based on the use of 1% resistors in critical locations. We'll identify these in the assembly diagrams, and show the bodies of the 1% resistors in light blue rather than the more usual light brown color.

2 X 22 Watt Stereo Amplifier Circuit Using IC TDA 1554

Posted by Micro System

on Friday, July 23, 2010

This is the circuit diagram of a powerful and high quality stereo amplifier using IC TDA 1554. The circuit has only very few components. The circuit works best with a 4 Ohm speaker. This is the figure of the circuit;


IC must be connected to a heat sink. A computer cabinet fan can also be used in addition(not necessary). Any way better the cooling better the performance. The circuit roughly draws 6A current at 12 V at full volume. So the power supply must be any thing more than 6A. Up to 18 V can be used ,which gives a bit more power boost. Commonly used is 12 V.

Parts List

R1 39K 1/4 Watt Resistor
C1,C2 10uf 25V Electrolytic Capacitor
C3 100uf 25V Electrolytic Capacitor
C4 47uf 25V Electrolytic Capacitor
C5 0.1uf 25V Ceramic Capacitor
C6 2200uf 25V Electrolytic Capacitor
U1 TDA1554 Two Channel Audio Amp Chip
MIS Heatsink For U1, Binding Posts (For Output), RCA Jacks (For Input)

Simple 2W amplifier circuit Using TDA7052

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This is a simple and humble of 2W amplifier suitable for small pocket radios and other portable audio gadgets.The circuit is based on Phillips Semiconductors IC TDA 7052.The amplifier can be run even from a 3V Mercury button cell. This is the figure of the circuit;

The IC TDA7052 is a mono output amplifier comng in a 8-lead DI package (DIP). The device is mainly designed for battery-operated portable audio circuits. The features of TDA 7052 include ,no external components needed, no switch-on or switch-off click sounds , great overall stability ,very low power consumption (quiescent current 4mA) , low THD, no heat sinks required and short-circuit proof. The gain of TDA 7052 is fixed internally at 40 dB. . To compensate the reduction of output power due to low voltage supply the TDA7052 uses the Bridge-Tied-Load principle (BTL) which can provide an output of around 1 to 2 W Rms(THD = 10%) into an 8 Ohm load with a power supply of 6 V. In the circuit the potentiometer can be used to control the volume.Capacitor C1 and C2 are meant for filtering the supplyvoltage if a battery eliminator is used as supply source. For operations using a battery C1 and C2 are no necessary.