12/26/2013

Overload Indicator TL072

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The overload indicator consists of a window comparator that measures the magnitude of an a.f. signal. Two of the opamps contained in an TL072 are supplied with a reference voltage by potential divider R1-R2-R3-P1. The outputs of the opamps drive T1 via diodes D1 end D2 (that function as half-wave rectifier), which in turn actuates D3. Network R5-R6-C2 ensures that the LED lights even during short signal peaks. Capacitor C2 is charged fairly rapidly via D1 (or D2)and R5, after which it discharges slowly via R6, R9 and the base-emitter junction of T1. Capacitor C1 also contributes to the longer lighting of the LED.
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     When the level of the signal at the input is high enough, IC1a, is toggled by the positive half periods of the signal and IC1b by the negative halves. In this way, a peak above the maximum level will be indicated even when the signal is asymmetrical. Because of the symmetrical power supply and design of the indicator, the reference voltage for both opamps can be set with one potentiometer. The circuit draws a current of 5-6 mA when the LED is off. When an overload peak is indicated, the LED draws an additional 20 mA. With values as shown, the reference voltage can be set roughly between 0.9 V and 5.5 V.
The circuit can be connected to the output of a power amplifier, but potential divider R7-R8 then needs to be adapted and protected by diodes to the supply lines.



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12/18/2013

BUZ23 MOSFET Audio Amplifier 1 x 240W

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BUZ23 MOSFET general description:

     A high power audio amplifier circuit which can output up to 240W on a 4Ω speaker.
This mosfet amplifier is built with BUZ23 and uses a 40V symmetrical power supply. Connect the NTC close to the heatsinker.

BUZ23 MOSFET circuit diagram:


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IRF9530 IRF530 Audio Amplifier 70 W

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IRF9530 IRF530 general description:
This simple power mosfet audio amplifier circuit, with TL071C and 2 MOSFETs (IRF9530 and IRF530) can deliver up to 45 Watts on 8 Ω speaker. This schematic is based on Siliconix application and on variations of voltage on the 2 resistors that are serial inserted on the voltage supplier of the operational amplifier driver. The MosFet transistor must be mounted on a heatsink with at least 1K/W.

Amplifier’s efficiency is 70%, distortions at cut frequency were at most 0.2% at 20Hz on 8 Ω and 10W. With a power supply of ± 30V the mosfet audio amplifier can deliver 45W on 8 Ω and 70w on 4 Ω. Remember that this audio amplifier is not protected on shortcircuits so everytime you switch on check to see if the speaker is connected.

IRF9530 IRF530 circuit diagram:


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FET Amplifier Configurations

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When using FETs as amplifiers, the input signal is applied across two  terminals of the FET and the output is taken across two terminals.

Three FET amplifier configurations:

  • common source,
  • common gate, and
  • common drain.

Common Source Amplifier

      The Common Source (CS) amplifier is the FET equivalent of the common  emitter transistor amplifier configuration. Like the CE amplifier, it is capable of high voltage gain. The CS amplifier has the input applied between the gate and source Terminals and the output signal taken across the drain and source terminals. Therefore, the source terminal is common to both the input and output signals.
Use of coupling capacitors CIN and COUT. Their function is to block the DC or bias current from entering the AC signal source and load resistor RL.Conversely, during AC operation they couple the AC signal source to the input of the amplifier and the resulting output to the load resistor. Bypass capacitor C1 is used to bypass the source resistor and increase the amplifier's voltage gain.

Self bias CS amplifier used previously, with the load resistance removed. Note the injection of an AC signal at the gate of the FET. With a BJT amplifier, an increase in the input signal resulted in an increase in the base current. A FET amplifier however, does not have any current flowing through the gate source junction. This is due to the reverse biased PN junction (JFETs) or the silicon dioxide insulating layer (MOSFETs).Applying an input signal has an amplitude of 2Vpk-pk. As the input signal goes more positive, the signal current flows through the gate resistor RG. This current flow develops a voltage drop across RG which equals the amplitude of the applied voltage ie VIN = VG.
With the gate voltage increasing from the quiescent condition (zero volts), the gate source voltage must be decreasing because the source voltage is a positive voltage. Remember, for an N channel JFET, VGS must be negative. A decreased or less negative VGS applied to the N channel JFET , results in the drain current increasing from the quiescent  condition. Note if VGS goes more negative ie -2 V to -4 V, VGS is said to be increasing. An increasing drain current produces a larger voltage drop across the drain resistor, resulting in less voltage at the output or drain terminal. With the input signal returning to zero volts, the FET amplifier is again at  the quiescent point. As the input signal goes more negative the process reverses, resulting in an increasing VGS and decreasing drain current.
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12/12/2013

Overload protection for speakers

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     Although the protection circuit is fairly simple, it forms an effective guard against overload of the input of amplifiers and loudspeakers. Why these inputs may need protection now that line levels have been standardized is because there are signal sources on the market that generate outputs of several volts instead of the standardized 1 V r.m.s. Also, in some applications, the loudspeaker signal is applied to the line output of a separate amplifier via a voltage divider, in which case the levels may be well above 1 V r.m.s. The diagram shows a schematic that resembles the familiar series resistor and zener diode. Here, however, the zener is constructed from a small rectifier and a transistor, since commercial zeners appear to start conducting way below their rated values, which gives rise to unwanted distortion. The constructed zener makes a well-defined limitation possible and does not affect signals below the critical level. Configuring T1 as a diode reduces the number of components needed to a minimum: not even a voltage divider or potentiometer is required. Measurements on the prototype show that the input signal remains virtually undistorted at levels up to 700 mV r.m.s. At the threshold of 1 V r.m.s., the distortion is about 0.02%. Above this level, limiting is welldefined. The peak output voltage of the circuit is about 3 V with an input voltage of about 13 V r.m.s. If the limiting level is required to be slightly higher, consideration should be given to replacing T1 by three or four cascaded diodes.
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Dual Voice Coil Subwoofers

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Dual voice coil subwoofers are becoming a popular choice among car audio enthusiasts who want more flexibility in
wiring their sound systems. While typical subwoofers have a single voice coil, dual voice coil (DVC) subwoofers use two separate voice coils, each with its own connections, mounted on one cylinder, connected to a common cone.

Parallel: A dual 4-ohm voice coil subwoofer with its coils wired in parallel presents a 2-ohm load to your amplifier. Since an amplifier produces more wattage at a lower impedance, the parallel connection ensures you'll get the most output from your amp. In the same fashion, if you have a stereo amplifier and two DVC subs, wire both subs for 2-ohm impedance (one per channel) for maximum output.The key difference between single and dual voice coil subwoofers is the multiple wiring options DVC subs offer:

  • Series: Series wiring lets you configure multiple woofers to one amplifier at an acceptable impedance. Wire both coils in series for an 8-ohm impedance, and then wire two 8-ohm subs together in parallel for 4-ohm total impedance (perfect for most 2-channel amps bridged to mono operation). Another example: if you have a high-powered 2-channel amplifier, wire four 8-ohm subs per channel (each channel sees a 2-ohm load).
  • Independent: You can wire each voice coil to a separate channel of your amplifier, if you prefer not to bridge your amp. Independent wiring is a nice option if you're wiring two DVC subs to a 4-channel amplifier — one voice coil per channel. Just make sure the signal going to each coil is exactly the same, or the differences will cause distortion.

DVCs and high-performance amplifiers


Also, if you choose to add an unregulated amp as a power upgrade to your existing DVC subwoofer system, you can simply rewire your subs for optimum impedance. Remember that most car amps are stable down to 2 ohms in normal operation, and to 4 ohms in bridged mode. It's important to check your amp's manual for its operating parameters before hooking up a DVC sub that's wired for low impedance.Some amplifiers are designed with an unregulated power supply — these amps are favored by mobile audio competitors for their superior performance. An unregulated amp's power increases dramatically when it sees a lower impedance load. For example, an amplifier that produces 75 watts RMS x 2 channels at 4 ohms would double its power to 150 watts x 2 with a 2-ohm load. DVC subwoofers (particularly the dual 2-ohm models) give you the flexibility to wring every bit of power out of this type of amplifier.

A DVC sub offers the same performance whether it's wired in series or parallel. Its power handling levels, frequency response, and other specifications do not change — the only difference is the impedance presented to the amplifier. As a result, you'll need to use the enclosure that's recommended for your sub, no matter how it's wired.
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Subwoofer Wiring Diagrams

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     A subwoofer or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as bass. The typical frequency range for a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound,and below 80 Hz in THX-approved systems. Subwoofers are intended to augment the low frequency range of loudspeakers covering higher frequency bands.


     Subwoofers are made up of one or more woofers mounted in a loudspeaker enclosure—often made of wood—capable of withstanding air pressure while resisting deformation. Subwoofer enclosures come in a variety of designs, including bass reflex (with a port or passive radiator in the enclosure), infinite baffle, horn-loaded, and bandpass designs, representing unique tradeoffs with respect to efficiency, bandwidth, size and cost. Passive subwoofers have a subwoofer driver and enclosure and they are powered by an external amplifier. Active subwoofers include a built-in amplifier.
Subwoofer Wiring Diagrams
Subwoofer Wiring Diagrams
                                                                                                                    from crutchfield.com
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12/10/2013

Op Amp Circuit Collection - Basic Circuits

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Op Amp Circuit Collection

Basic Circuits


Inverting Amplifier

Inverting Amplifier
Inverting Amplifier
Non Inverting Amplifier
Non Inverting Amplifier
Non Inverting Amplifier
Diference Amplifier
Diference Amplifier
Diference Amplifier
Inverting Summing Amplifier

Inverting Summing Amplifier
Inverting Summing Amplifier
Non-Inverting Summing Amplifier
Non-Inverting Summing Amplifier
Non-Inverting Summing Amplifier

Inverting Amplifier with High Input Impedance
Inverting Amplifier with High Input Impedance
Inverting Amplifier with High Input Impedance

Fast Inverting Amplifier with High Input Impedance
Fast Inverting Amplifier with High Input Impedance
Fast Inverting Amplifier with High Input Impedance

Non-Inverting AC Amplifier
Non-Inverting AC Amplifier
Non-Inverting AC Amplifier

Practical Differentiator
Practical Differentiator
Practical Differentiator

 Integrator
Integrator
Integrator

Fast Integrator
Fast Integrator
Fast Integrator

Current to Voltage Converter
Current to Voltage Converter
Current to Voltage Converter

Circuit for Operating the LM101 without a Negative Supply
Circuit for Operating the LM101 without a Negative Supply
Circuit for Operating the LM101 without a Negative Supply

Circuit for Generating the Second Positive Voltage
Circuit for Generating the Second Positive Voltage
Circuit for Generating the Second Positive Voltage

Neutralizing Input Capacitance to Optimize Response Time
Neutralizing Input Capacitance to Optimize Response Time
Neutralizing Input Capacitance to Optimize Response Time

Voltage Comparator for Driving DTL or TTL Integrated Circuits
Voltage Comparator for Driving DTL or TTL Integrated Circuits
Voltage Comparator for Driving DTL or TTL Integrated Circuits

Integrator with Bias Current Compensation
Integrator with Bias Current Compensation
Integrator with Bias Current Compensation

Double-Ended Limit Detector
Double-Ended Limit Detector
Double-Ended Limit Detector

Multiple Aperture Window Discriminator
Multiple Aperture Window Discriminator
Multiple Aperture Window Discriminator

Offset Voltage Adjustment for Inverting Amplifiers UsingAny Type of Feedback Element
Offset Voltage Adjustment for Inverting Amplifiers UsingAny Type of Feedback Element
Offset Voltage Adjustment for Inverting Amplifiers UsingAny Type of Feedback Element

Offset Voltage Adjustment for Non-Inverting Amplifiers Using Any Type of Feedback Element
Offset Voltage Adjustment for Non-Inverting Amplifiers Using Any Type of Feedback Element
Offset Voltage Adjustment for Non-Inverting Amplifiers Using Any Type of Feedback Element

Offset Voltage Adjustment for Voltage Followers
Offset Voltage Adjustment for Voltage Followers
Offset Voltage Adjustment for Voltage Followers

Offset Voltage Adjustment for Differential Amplifiers
Offset Voltage Adjustment for Differential Amplifiers
Offset Voltage Adjustment for Differential Amplifiers

Offset Voltage Adjustment for Inverting Amplifiers Using 10 kΩ Source Resistance or Less

Offset Voltage Adjustment for Inverting Amplifiers Using 10 kΩ Source Resistance or Less
Offset Voltage Adjustment for Inverting Amplifiers Using 10 kΩ Source Resistance or Less




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