|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
25th Feb 2020, 2:13 pm | #21 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
|
Re: Large Value Inductor Question
If it's amplifying an AM-modulated carrier, the amplifier needs to be operating linearly. Class-A or (at a pinch) class-B, but definitely not class-C!
|
25th Feb 2020, 2:16 pm | #22 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
|
Re: Large Value Inductor Question
Quote:
Consider a simple mains transformer. SRF is likely to be around 5kHz. With typical primary inductance 10H (giving 80mA magnetising current), that implies a winding capacitance of 20nF. Now suppose that the core manufacturer found some fantastic new alloy, same price, which upped the inductance to 1,000,000H of all transformers it was used in, with no other effects. It's easy to see the world would be delighted, magnetising currents would disappear to practically zero. It's also easy to see that the new SRF would be 0.35Hz. We're running at 50Hz!! But does it matter? No. In the current example, if the choke's SRF is a bit below the operating frequency, it just means a little readjustment of the ATU. And if the SRF is below operating frequency, not because of high stray capacitances, but because of a super-high permeability core, then that readjustment will be miniscule. Where it might matter, is if there is feedback. Changing an inductive reactance to capacitive may make the difference between stability and instability. But in this circuit... Nope. |
|
25th Feb 2020, 5:20 pm | #23 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
|
Re: Large Value Inductor Question
If you want a couple of proper RF transistors one rung up the power ladder, PM me an address and I'll stick a couple of 2N3866 in a jiffy bag for you.
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
25th Feb 2020, 7:53 pm | #24 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
|
Re: Large Value Inductor Question
Ah yes! The good ol' 2N3866. I first met these during a project in 1967 - and have been using them, albeit occasionally, ever since.
Al. |
26th Feb 2020, 11:28 am | #25 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
|
Re: Large Value Inductor Question
Thanks very much for that David, have sent you a PM. I’ll have a look online at some circuits using them
|