Hi everyone, I’m hoping that you can help with something that is a bit of a poser for your humble narrator. I just received an email from my chum Glenn Kirilow, who hails from Down Under. In his message, Glenn spake as follows:
G’day Max, quick one for you. I have a real interest in high-speed analog design, a field I feel is criminally underappreciated. Sadly, in university 10 years back now, the final area we touched on was current feedback op-amps. We didn’t have any subjects on RF circuits etc., which was a real shame.
Are there any books or materials you would recommend on the topic? I’ve just been reading app notes from TI and Analog Devices as well as various websites but would be great to have a reference too. I’ve got The Art of Electronics 3rd edition, which is great, but I need to go a step further.
The problem here is that, as I’ve mentioned on occasion, I’m a digital logic engineer by trade and I tend to find the wibbly-wobbly nature of analog signals to be a tad disquieting. So, with Glenn’s permission, I decided to post this plaintive plea in the heartfelt hope that someone wiser than I would have a clue. Are you that someone?
I assume this is not about RF receivers and transmitting techniques ! But about linear processing of analog signal at high frequencies.
Application notes from the linear IC manufacturers can be a great starting point. most are for free downloadable.
Hi Gert — thanks for the feedback — Max
That is correct Gert. Yes, I regularly read through these, I particularly like the notes from Linear Tech and Analog Devices!
“Analysis and Design of Analog Integrated Circuits” by Paul R. Gray and Robert G. Meyer, John Wiley & Sons, Inc. The material also applies to discrete designs. This book taught me to treat NPN transistors as voltage-controlled devices, like JFETs with ridiculously-high transconductance Gfs = Iemitter/26mV.
Remember that inductance is everywhere, so knowledge of RF techniques can be useful for preventing parasitic oscillation. For example, emitter followers exhibit inductive output impedance due to current gain dropping with rising frequency. This inductance resonates with stray capacitance to resonate in the VHF range, enabling parasitic oscillation. This can be a problem even in low-speed circuits, as modern devices are faster than their old equivalents.
Great advice as always — thanks Peter
I have not read the book mentioned, I shall have a read of it! Sounds like exactly what I was after, thanks!
Yes great points, I should refresh my RF knowledge base too.
Since high speed digital design is analog, there may be some relevant information in all publications by Howard Johnson especially “High Speed Digital Design” ( https://www.amazon.ca/High-Speed-Digital-Design-Handbook/dp/0133957241 )
Here’s a suggestion though- if Glenn can’t find the subject matter he wants, he should write his own book. Working through issues and research will give him the basis, chapter by chapter.
If Glenn wants such a book, surely others need it as well.
Oooh — now there’s an idea — and since it doesn;t require any effort on my part, I’m all for it 🙂
Hi Aubrey. I have heard of Howard’s book, I shall take a look.
Funny you mention that, I was just thinking recently I should write a book on this topic, good to hear someone else say it too and I agree agrees would definitely need it!!
When testing a new analog design, try waving your hand very close to the circuitry without touching the circuitry. If the circuit’s behavior changes, you likely have an RF parasitic oscillation, or a sensitivity to radio-station pickup.
If your circuit is noisier than it should be, suspect RF parasitics or pickup. If the noise is in the audio frequency range, listen to the noise. Can you hear music in the noise? If you hear music, check for a 19-kHz spectral line: the FM-stereo pilot tone.
Dead-bug ugly construction, where unetched copper-clad board is used as the ground plane and leads are kept short, is excellent for prototyping. Dead-bug refers to chips placed on their backs on the copper plane with their leads sticking up in the air. Solder wire-leaded bypass capacitors between power pins and the ground plane with zero lead length. SMT capacitors will work, but tend to fracture apart. Solder mimimum lead length wires between ground pins and the ground plane.
I recall teaching these techniques to colleagues over fifty years ago.
Hi Peter — this is awesome advice — you should write a book yourself!!!
I recall learning these techniques 50 years ago. Were you my teacher? LOL
Analog brain-teaser: What current flows through the insulating dielectric of a capacitor? I plan to post the answer in a few days.
I await in dread antici…
There is also Eric Bogatin’s book
Signal and Power Integrity
I’ve not read this book, but Eric is awesome.
Maxwell’s displacement current flows through the insulating dielectric of a capacitor.