Talk:Hartley oscillator

message: I think the tube based Scott 310E oscillator should be replaced with a more modern BJT or FET version. The audience for these articles probably knows very little about tubes (myself included) and the schematic is more confusing than helpful. -Roger 20:00, 31 October 2007 (UTC)
thread_title:  Scott 310E oscillator schematic 

message: Presumably the oscillator requires either a valve or a transistor but there is no mention of this in the article. Biscuittin (talk) 23:09, 1 March 2008 (UTC)
thread_title:  Missing item 

message: There is much hearsay that the circuit is not suitable to generate a pure sine wave. This is simply not true for a properly designed circuit; it depends on the place where the signal is obtained. The signal on the coil tap is rather good, if the amplifier is not too much overloaded, i.e. the tap is small enough; then, the source is of relatively low amplitude and impedance. Or a low capacity buffer can to be used at the hot end of the coil (see the EDN article, where the buffer is coupled to the gate and not the source, as is often shown elsewhere).
Because using the LC circuit as a source gives problems with (capacitive) load and stability, often the current of the amplifier is used directly or indirectly. This waveform, however, is normally far away from a sine wave. But this is true for practically every LC oscillator, unless its gain is controlled by amplitude stabilisation.
Otherwise, I would be interested in reliable references.
 
-- Rainglasz (talk) 09:54, 10 December 2008 (UTC)
thread_title:  Disadvantages 

message: The original text placed too much emphasis on the requirement of an inductive feedback voltage divider. This is very misleading as the Hartley oscillator does not require such a connection. 
Kevin aylward (talk) 16:32, 26 December 2012 (UTC)
thread_title: Basic Theory

message: This circuit looks wrong to me.  It appears that the JFET's junction will be forward-biased during at least part of the cycle.  Isn't that usually a no-no?  Also, I notice that most other JFET circuits on the internet have this same flaw.  I'm beginning to wonder whether everyone else is wrong or I was just taught wrong.  Would it be possible to make this a depletion-mode MOSFET instead to solve the problem?  Xezlec (talk) 19:56, 20 January 2013 (UTC)
replies: text: As a simplified circuit, it's probably OK. The forward bias on the junction would work as an amplitude limiter; amplifier gain would decrease. Some real circuits may have a form of grid leak bias, but I think the junction is still overdriven. It's been too long. Some circuits use a diode to ground to avoid forward biasing the junction, but those designs may have poor noise performance. Glrx (talk) 01:56, 5 February 2013 (UTC)
replies: text: I added a practical example. I used the grid leak from the original schematic to give the JFET proper bias, but I did not include the diode. There is no "correct" solution. AndreAdrian (talk) 21:26, 19 February 2024 (UTC)

text: Simulation with LTSpice gives easy oscillation and breadboarding of circuit was a success after I increased C2 from 4.7pF to 10pF. AndreAdrian (talk) 14:36, 20 February 2024 (UTC)
thread_title:  Circuit is wrong? 

message: The article appears to contain some significant errors:
1 The simplified circuit is described as providing feedback from the inductor tap, the source of the FET. Since the gate is the input terminal to the FET, that surely is the feedback 'output' from the LC circuit. The tap is the input in this configuration, driven by the low-impedance source;
2 The polarity marking on the op-amp version is reversed; 
* I really wonder whether this opamp circuit, even after correction (it would not work properly as-is) is widely recognised as truely "Hartley"... meanwhile a common-base version of tapped-coil oscillator is quite often referred to as "Hartley" yet not mentioned here... until now. Maitchy (talk) 21:52, 25 November 2013 (UTC)
thread_title:  Several errors 

message: I don't have time to go into it, but the simplified circuit description has many flaws. If the common drain amplifier is a voltage controlled voltage source, then it would destroy the tank Q. Tap selection is much more involved. JFET will limit amplitude. JFET input Z inf only at low freq. Glrx (talk) 17:39, 14 August 2015 (UTC)
thread_title:  Circuit operation 

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thread_title:  External links modified 

message: It is not clear to me how this article should approach the subject. I understand it is not intended to be a tutorial.
Do any actual real-world implementations belong here? Or should the approach be a generic one -- for example a circuit model containing only a generic transconductance for instance? 
Or should it contain both? First a presentation of a generic circuit, not specific to any particular technology, followed by some examples of implementation in various technologies (e.g. vacuum tube triode, jfet, bipolar transistor, op-amp, etc)?
It seems to me the presentation of a generic circuit with a VCCS (transconductance) can be used to show not only the operation of the circuit, but to analyze the necessary conditions for oscillation to occur (e.g. RHP poles in a transfer function).
Anyone interested in seeing that? 142.254.37.91 (talk) 18:01, 7 March 2023 (UTC)
thread_title:  General approach to article