Showing posts with label amp. Show all posts
Showing posts with label amp. Show all posts
Friday, November 1, 2013
Voltage Feedback Op Amp
VOLTAGE FEEDBACK OPERATIONAL AMPLIFIER
Device Description:
Voltage feedback operational amplifiers usually manufactured for industrial use have ultra-low power requirements, with a typical quiescent current value of approximately 250 micro amperes. The typical current drawn in powered-down mode for such an amplifier is 0.5 micro amperes. They are suitable for operation at any bandwidth below 56 MHz. The manufacturing process is called a SiGe complimentary bipolar process. It is an advanced method used at the industrial level.
Ultra-low power-op amps have rail-to-rail output along with negative rail input. They are specially designed to operate under an EMF ranging from 2.5 – 5.5 Volts. There are two options: the single or dual supply operational amplifier. The aforementioned voltage supply is for single mode op amps whereas for a dual mode operational amplifier the power supply ranges from -1.25 to -2.25 Volts and 1.25 to 2.75 Volts (in dual supply configuration). These operational amplifiers are leading the industry due to their high power/performance ratio. They consume a mere 250 micro amperes of current on each channel, under a unity gain of 56 MHz.
A voltage feedback operational amplifier is well-suited for portable battery applications in which low power consumption is desired along with good performance. It consumes little power, yet offers high frequency performance. Such operational amplifiers serve as the device with high frequency performance in many battery-powered applications by lowering current consumption. This is achievable on account of a power saving mode, in which its current consumption can be lowered to 1.5 micro amperes. A voltage feedback operational amplifier consists of an integrated gain setting resistor in its both single and dual supply variants. These gain setting resistors are bound to a printed circuit board with the smallest possible size across a wide range of attainable gain values - they can be replaced with a potentiometer for controllable resistance. The design of a voltage feedback operational amplifier impacts the range of attenuation values. These amplifiers are designed to work at industrial-standard temperatures ranging from -40 to 250 degrees centigrade.
Applications of Voltage Feedback Operational Amplifiers
A voltage feedback operational amplifier has many industrial applications, including the following:
• Audio ADC input buffers
• Portable systems
• High density systems
• Low power systems
• Ultrasonic flow systems
• ADC Drivers
• Low power SAR
• Low power signal conditioning systems.
Device Description:
Voltage feedback operational amplifiers usually manufactured for industrial use have ultra-low power requirements, with a typical quiescent current value of approximately 250 micro amperes. The typical current drawn in powered-down mode for such an amplifier is 0.5 micro amperes. They are suitable for operation at any bandwidth below 56 MHz. The manufacturing process is called a SiGe complimentary bipolar process. It is an advanced method used at the industrial level.
Ultra-low power-op amps have rail-to-rail output along with negative rail input. They are specially designed to operate under an EMF ranging from 2.5 – 5.5 Volts. There are two options: the single or dual supply operational amplifier. The aforementioned voltage supply is for single mode op amps whereas for a dual mode operational amplifier the power supply ranges from -1.25 to -2.25 Volts and 1.25 to 2.75 Volts (in dual supply configuration). These operational amplifiers are leading the industry due to their high power/performance ratio. They consume a mere 250 micro amperes of current on each channel, under a unity gain of 56 MHz.
A voltage feedback operational amplifier is well-suited for portable battery applications in which low power consumption is desired along with good performance. It consumes little power, yet offers high frequency performance. Such operational amplifiers serve as the device with high frequency performance in many battery-powered applications by lowering current consumption. This is achievable on account of a power saving mode, in which its current consumption can be lowered to 1.5 micro amperes. A voltage feedback operational amplifier consists of an integrated gain setting resistor in its both single and dual supply variants. These gain setting resistors are bound to a printed circuit board with the smallest possible size across a wide range of attainable gain values - they can be replaced with a potentiometer for controllable resistance. The design of a voltage feedback operational amplifier impacts the range of attenuation values. These amplifiers are designed to work at industrial-standard temperatures ranging from -40 to 250 degrees centigrade.
Applications of Voltage Feedback Operational Amplifiers
A voltage feedback operational amplifier has many industrial applications, including the following:
• Audio ADC input buffers
• Portable systems
• High density systems
• Low power systems
• Ultrasonic flow systems
• ADC Drivers
• Low power SAR
• Low power signal conditioning systems.
Thursday, September 19, 2013
Build an op amp with three Discrete Transistors
You can use three discrete transistors to build an operational amplifier with an open-loop gain greater than 1 million (Figure 1). You bias the output at approximately one-half the supply voltage using the combined voltage drops across zener diode D1, the emitter-base voltage of input transistor Q1, and the 1V drop across 1-MΩ feed-back resistor R2.
Resistor R3 and capacitor C1 form a compensation network that prevents the circuit from oscillating. The values in the figure still provide a good square-wave response. The ratio of R2 to R1 determines the inverting gain, which is −10 in this example.
You can configure this op amp as an active filter or as an oscillator. It drives a load of 1 kΩ. The square-wave response is good at 10 kHz, and the output reduces by 3 dB at 50 kHz. Set the 50-Hz low-frequency response with the values of the input and the output capacitors. You can raise the high-frequency response by using faster transistors and doing careful layout. Link
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| Figure 1. | This ac-coupled inverting op amp has an open-loop gain of 1 million. R1 and R2 set a closed-loop gain of −10. |
Resistor R3 and capacitor C1 form a compensation network that prevents the circuit from oscillating. The values in the figure still provide a good square-wave response. The ratio of R2 to R1 determines the inverting gain, which is −10 in this example.
You can configure this op amp as an active filter or as an oscillator. It drives a load of 1 kΩ. The square-wave response is good at 10 kHz, and the output reduces by 3 dB at 50 kHz. Set the 50-Hz low-frequency response with the values of the input and the output capacitors. You can raise the high-frequency response by using faster transistors and doing careful layout. Link
Monday, September 16, 2013
10 Amp Solar Charge Controller
The SCC2 is a solar charge controller, its function is to regulate the power flowing from a photovoltaic panel into a rechargeable battery. It features easy setup with one potentiometer for the float voltage adjustment, an equalize function for periodic overcharging, and automatic temperature compensation for better charging over a range of temperatures.
10 Amp Solar Charge Controller Circuit Diagram with Parts List
The goal of the circuit design was to make a charge controller with analog simplicity, high efficiency, and reliability. A medium power solar system can be built with a 12V solar panel up to 10 amps, the SCC2, and a rechargeable battery. The SCC2 works with lead acid, NiCD and NiMH batteries with ratings from less than one to several hundred amp-hours. With the appropriate parts selection, the SCC2 can be operated at 6V, 12V, 24V or other voltages.
Specifications:
The SCC2 acts as a medium power DC current switch between the + terminals of the PV and battery. Diode D1 prevents reverse night time current flow from the battery back to the PV panel.
When the PV voltage is high enough to charge the battery, zener diode D2 conducts and turns on transistor Q2. Q2 switches the power for the rest of the circuit on. The circuit is switched off at night. IC2 provides a 5 volt regulated voltage to power the comparator circuits, it also provides a reference voltage for comparator IC1a.
When the battery voltage is below the desired full voltage and needs charging, comparator IC1a turns on and activates Q1 and Q3, this allows the solar charging current to flow into the battery. Note that Q3 is a P-channel mosfet, this allows the circuit to be wired with a common ground for the solar panel and battery. The solar current loop is drawn in heavy lines on the schematic.
When the battery reaches the full charge point, IC1a operates as a comparator based schmidt trigger oscillator, it switches the solar current off and on. The switching causes the battery voltage to oscillate a few tens of millivolts above and below the desired set point. A rail-to-rail op-amp is required for proper operation, 741 style op-amps will not work in this circuit.
The red/green charging/full LED is driven between the output of IC1a and IC1b. IC1b has an inverted version of the IC1a signal. Pin 5 of IC1b only needs an approximate center point to work as an on-off comparator, it is connected to the varying IC1a pin 2 so that it does not require another reference divider circuit.
The resistors and thermistor on the input side of IC1a form a resistive bridge circuit that is used to compare the battery voltage to a reference voltage coming from IC2/R8/R9. The potentiometer adjusts the voltage point around which the circuit will oscillate on full charge. Resistor R7 adds positive feedback to IC1a for a schmidt trigger characteristic and C6 sets the maximum frequency of oscillation. The thermistor provides thermal compensation, as the temperature goes down, the float voltage setting goes up.
The equalize switch, S1a, forces the circuit on for intentional overcharging. Switch S1b and R1 can be used to select a different float voltage range, you can experiment with this by using different values of R1, typically R1 should be greater than 1M.
Alignment:
Connect the solar panel to the SCC2 solar panel input connectors, connect the battery to the SCC2 output connectors. Put the solar panel in the sun, and watch the battery charge up. Systems where the battery is frequently discharged way down should occasionally be run in equalize mode for a few hours or a full day. It is best to monitor the battery voltage during this operation, disable equalization if the battery voltage goes above 16V (12V version).
10 Amp Solar Charge Controller Circuit Diagram with Parts List
The goal of the circuit design was to make a charge controller with analog simplicity, high efficiency, and reliability. A medium power solar system can be built with a 12V solar panel up to 10 amps, the SCC2, and a rechargeable battery. The SCC2 works with lead acid, NiCD and NiMH batteries with ratings from less than one to several hundred amp-hours. With the appropriate parts selection, the SCC2 can be operated at 6V, 12V, 24V or other voltages.
Specifications:
- Maximum solar panel current: 10 Amps
- Night time battery drain current: approximately 1ma
- Nominal battery voltage: 6V, 12V or 24V.
- See the full SCC2 specifications for more information.
The SCC2 acts as a medium power DC current switch between the + terminals of the PV and battery. Diode D1 prevents reverse night time current flow from the battery back to the PV panel.
When the PV voltage is high enough to charge the battery, zener diode D2 conducts and turns on transistor Q2. Q2 switches the power for the rest of the circuit on. The circuit is switched off at night. IC2 provides a 5 volt regulated voltage to power the comparator circuits, it also provides a reference voltage for comparator IC1a.
When the battery voltage is below the desired full voltage and needs charging, comparator IC1a turns on and activates Q1 and Q3, this allows the solar charging current to flow into the battery. Note that Q3 is a P-channel mosfet, this allows the circuit to be wired with a common ground for the solar panel and battery. The solar current loop is drawn in heavy lines on the schematic.
When the battery reaches the full charge point, IC1a operates as a comparator based schmidt trigger oscillator, it switches the solar current off and on. The switching causes the battery voltage to oscillate a few tens of millivolts above and below the desired set point. A rail-to-rail op-amp is required for proper operation, 741 style op-amps will not work in this circuit.
The red/green charging/full LED is driven between the output of IC1a and IC1b. IC1b has an inverted version of the IC1a signal. Pin 5 of IC1b only needs an approximate center point to work as an on-off comparator, it is connected to the varying IC1a pin 2 so that it does not require another reference divider circuit.
The resistors and thermistor on the input side of IC1a form a resistive bridge circuit that is used to compare the battery voltage to a reference voltage coming from IC2/R8/R9. The potentiometer adjusts the voltage point around which the circuit will oscillate on full charge. Resistor R7 adds positive feedback to IC1a for a schmidt trigger characteristic and C6 sets the maximum frequency of oscillation. The thermistor provides thermal compensation, as the temperature goes down, the float voltage setting goes up.
The equalize switch, S1a, forces the circuit on for intentional overcharging. Switch S1b and R1 can be used to select a different float voltage range, you can experiment with this by using different values of R1, typically R1 should be greater than 1M.
Alignment:
- Start with a charged battery, connect the solar panel directly to the battery until the battery voltage is at or above the desired full setting, this also that the panel is capable of charging the battery.
- While measuring the battery voltage, adjust VR1 clockwise to align the float voltage set point. If the LED turns red before it reaches the desired float voltage, the battery will need to charge for a while.
- When the battery is fully charged, it should be at the float voltage and the led should show alternating colors.
- The float voltage should be set when the board and battery are at room temperature. Typical 12V set points are 13.8V for a gell cell and 14.5V for a wet cell. For 6V, divide those by two, for 24V, multiply by 2.
- Follow your battery manufacturers recommendations for the best settings.
- Readjust the float voltage after the battery has reached a full charge.
- The float voltage should be set when the circuit is at room temperature.
Connect the solar panel to the SCC2 solar panel input connectors, connect the battery to the SCC2 output connectors. Put the solar panel in the sun, and watch the battery charge up. Systems where the battery is frequently discharged way down should occasionally be run in equalize mode for a few hours or a full day. It is best to monitor the battery voltage during this operation, disable equalization if the battery voltage goes above 16V (12V version).
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