by Roy McCammon:
The traditional three op-amp differential amplifier’s signal to noise ratio can be improved by 6dB by adding a resistor and slightly changing the connections. There is a trade-off though: The traditional topology has a high input impedance, whereas the low-noise version has a lower input impedance.
Differential amp has 6dB lower noise, twice the bandwidth – [Link]
by University of Bristol:
A breakthrough in the design of signal amplifiers for mobile phone masts could deliver a massive 200MW cut in the load on UK power stations, reducing CO2 emissions by around 0.5 million tonnes a year.
Funded by the Engineering and Physical Sciences Research Council (EPSRC), the Universities of Bristol and Cardiff have designed an amplifier that works at 50 per cent efficiency compared with the 30 per cent now typically achieved.
Currently, a 40W transmitter in a phone mast’s base station* requires just over 130W of power to amplify signals and send them wirelessly to people’s mobiles. The new design, however, enables the transmitter to work effectively while using just 80W of power.
New design for mobile phone masts could cut carbon emissions – [Link]
w2aew @ youtube.com writes:
A tutorial on the basics of an inverting and non-inverting summing amplifier using an op amp. The video assumes a basic knowledge of how inverting and non-inverting amplifiers using op amps work. If you are unfamiliar with this, I’d recommend viewing my video on how to easily understand the operation of most opamp circuits: https://www.youtube.com/watch?v=K03Rom3Cs28
Basics of an Op Amp Summing Amplifier – [Link]
This 1w audio amplifier circuit is designed using NCP2830 audio IC manufactured by ON Semiconductor. This audio power amplifier ic designed for portable communication device applications and require few external electronic components. NCP2830 is capable to provide 1W continuous output power in 8 ohms load. NCP2830 audio power amplifier main features are : high quality audio (THD+N = 0.04%) , low noise: SNR up to 100 dB, overall system efficiency optimization: up to 89% , Superior PSRR (−88 dB): Direct Connection to Battery , Very Low Quiescent Current 7 mA , Optimized PWM Output Stage: Filterless Capability , Selectable gain of 2 V/V or 4 V/V .
1W audio amplifier circuit using NCP2830 – [Link]
This DIY 300B triode amplifier project was completed by Stamou Tasos who is from Greece. Giovanni Militano and Stamou Tasos write:
As a thank you for the 300B amplifier schematics, Stamou has shared with us his implementation of the 300B single-ended (SE) tube amplifier schematic by J.C. Morrison. I have assisted by translating, formating and presenting his DIY 300B triode amplifier project.
The circuit that I decided to follow for my 300B triode amplifier I found on this site, the 300B Single-Ended (SE) tube amplifier schematic with direct coupled 6SN7 input stage. Please take a look at the SE 300B schematic for a description of Mr. J.C. Morrison’s SE 300B tube amplifier circuit which I will refer to as the “original schematic”. Specifically recommended in the circuit notes was that premium output transformers and components be used for the 300B amplifier build. For this SE 300B triode tube amplifier build I have used premium parts throughout, Lundahl audio output transformers and a DIY chassis. This 300B Single-Ended-Triode (SET) amplifier circuit uses a direct coupled 6SN7 driver stage. The output stage is a SE 300B triode and the maximum power output is about 8 Watts per channel. A pair of reasonably sensitive (~91 dB+) loudspeakers will be required with this 300B SET amplifier.
DIY 300B Single-Ended-Triode (SET) Hi-Fi Amplifier – [Link]
Industry’s Widest Range Current-Sense Amplifier Measures 10mA to 10A without Increasing Measurement Errors
The MAX44284 is a high-side, current-sense amplifier that operates with a 1.7V to 5.5V single supply and is optimized for very low power operation with only 21µA of quiescent current.
The MAX44284 offers precision accuracy specifications of 2µV VOS and gain error of 0.05% (max). The device features an input common-mode voltage range from -0.1V to +36V. This current-sense amplifier has a voltage output and is offered in four different gain versions.
MAX44284 – 36V, Input Common-Mode, High-Precision, Low-Power Current-Sense Amplifier – [Link]
Make your own computer speaker system. This simple and inexpensive project will let you set up a small audio amplifier circuit and let more sound out your computer.
A simple audio amplifier circuit based on the LA4440 IC. This circuit will take your computer’s headphone level output and amplify it to drive a pair of external speakers. If you are listening to music or movies on laptops and computers, this is a useful little project for you. Laptop speakers are never loud enough to give satisfying listening. They give users the ability to hear something, but for anything like music or movie soundtracks they are very poor performers. The output from a laptops built in speakers is just too low, and this circuit addresses that low power with some additional amplification.
This circuit uses an LA4440 and some supporting components to give you much more power, while retaining a small package that you can use. The LA4440 is a dual channel audio power amplifier, with low distortion, and a good frequency range. Using 2 channels, the LA4440 will output 6 watts per channel, that can drive much larger speakers than a laptop can hold. When you set up a small enclosure(s), a 12V power supply, and an audio jack connection to the laptop you’ll have a nice enhancement to your laptop audio enjoyment.
Laptop Audio Amplifier – [Link]
Medical grade hearing aids are very expensive, if a person needs help hearing but not necessarily the full cost and capability of a prescribed hearing aid, this might be an option.
This is a less expensive, and DIY option for a hearing aid. It is not a substitute for a real hearing aid that an audiologist would prescribe. Amplification of all sounds and frequencies, or constant use in loud environments can cause additional hearing loss. This circuit could be helpful for some types of hearing loss and occasional use, as well as fill in during the average amount of time people wait to get a hearing aid (7 years).
The condenser microphone picks up acoustic signals, that then pass through the preamplifier stage composed of Q1, a BC547 transistor and a few resistors and a capacitor. The output from the BC547 preamplifier is then fed into the input for the amplifier circuit through the variable resistor R1 and C2. IC1 is the amplifier, a TDA2822M which is designed for low-power portable applications, and in this case, the output is bridged to drive the single earphone. A small LED is included to indicate power status and hopefully remind you to turn it off when you take it out.
A Low Cost Hearing Aid – [Link]
By Bill Schweber:
In a wireless design, two components are the critical interfaces between the antenna and the electronic circuits, the low-noise amplifier (LNA) and the power amplifier (PA). However, that is where their commonality ends. Although both have very simple functional block diagrams and roles in principle, they have very different challenges, priorities, and performance parameters.
How so? The LNA functions in a world of unknowns. As the “front end” of the receiver channel, it must capture and amplify a very-low-power, low-voltage signal plus associated random noise which the antenna presents to it, within the bandwidth of interest. In signal theory, this is called the unknown signal/unknown noise challenge, the most difficult of all signal-processing challenges.
Understanding the Basics of Low-Noise and Power Amplifiers in Wireless Designs – [Link]
Bruno Putzeys writes:
I hate articles titled “Ten … myths debunked.” I would have to start by listing a round number of clumsily worded claims by the non-feedback camp who probably never said any such thing, and juxtapose some simplified school-book explanations to put them right. And after shooting, flaying and roasting alive my straw men and generally hammering home that feedback doesn’t work like that, I should then fail to explain why not. This would leave an excellent status quo where everyone has had their say and truths remain somewhere in the middle.
Negative feedback in audio amplifiers: Why there is no such thing as too much – [Link]