OpAmps 101

Dave at EEVBlog explains what Operational Amplifiers (OpAmps) are and how they work. The concepts of negative feedback, open loop gain, virtual grounds and opamp action. The comparator, the buffer, the inverting and non-inverting amplifiers, the differential amplifier, and the integrator circuit configurations are also explained.
Then a practical breadboard circuit to demonstrate a virtual ground and the effect of voltage rail limitations.

Source: eevblog

Logic Pirate from Dangerous Prototypes

Logic Pirate by Dangerous Prototypes

The Logic Pirate is an inexpensive yet capable open source logic analyzer. For just 30 bucks it can sample 8 channels, 256K samples per channel, at a blazing (overclocked!) 60 MILLION samples per second! It’s designed to support the SUMP logic analyzer protocol on Jawi’s open source software that works on most platforms.

Its big brother the Logic Sniffer is great, but this little one looks more appropriate for simpler sniffing of all digital things, and more portable (always appreciated for hackers on the move).

Source: Dangerous Prototypes.

Layout design for NPO capacitors


Some NPO (Non-POlarized) capacitors may have a stripe on their package. Since this can’t be a polarization indication, you might wonder what it means.

A capacitor is made of two conductive elements separated by a non conductive element. In cylindric capacitors (both radial and axial), there is a central core for one conductive element, and an outer shell that makes the second, with some non-conductive substrate in the middle.

The mark on an NPO point to the outer shell. This can be interesting if you need an end of your cap to be grounded. Grounding the outer shell provides isolation from EMI and prevents noise getting in the capacitor.

Check out the layout design tips and tricks that can take advantage of this.

Source: Hack a Day.


Audio Transformers article from Jensen

Here is an extract from the book Handbook for Sound Engineers about audio transformers, from Jensen engineer Bill Whitlock.

Audio Transformers chapter from Handbook for Sound Engineers.


Since the birth of audio electronics, the audio transformer has played an important role. When compared to modern miniaturized electronics, a transformer seems large, heavy, and expensive but it continues to be the most effective solution in many audio applications. The usefulness of a transformer lies in the fact that electrical energy can be transferred from one circuit to another without direct connection, and in the process the energy can be readily changed from one voltage level to another.