Quantcast ARMSTRONG OSCILLATOR - 14181_77

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
2-13 increase in the oscillating frequency, and an increase in emitter voltage causes a decrease in the oscillating frequency. This is a result of the change in capacitance between the junctions of the transistor. However, a common bias source does not completely compensate since the effects on other circuit parameters of each bias voltage differ. Just as in any transistor circuit, changes in the transistor operating point and changes in temperature are encountered in the transistor oscillator. The effects of changes in temperature are to cause collector current to increase if the transistor is not stabilized. The increase in collector current can be prevented by reducing the forward bias. AMPLITUDE STABILITY The AMPLITUDE STABILITY of a transistor oscillator indicates the amount by which the actual output amplitude varies from the desired output amplitude. The same parameters (voltages and currents) that affect frequency stability also affect amplitude stability. Output amplitude may be kept relatively constant by ensuring that the feedback is large enough that the collector current is maintained at the proper level. Feedback used in this manner makes the output voltage directly proportional to the supply voltage. Thus, regulation of the supply voltage ensures good amplitude stability. ARMSTRONG OSCILLATOR The ARMSTRONG OSCILLATOR is used to produce a sine-wave output of constant amplitude and of fairly constant frequency within the rf range. It is generally used as a local oscillator in receivers, as a source in signal generators, and as a radio-frequency oscillator in the medium- and high-frequency range. The identifying characteristics of the Armstrong oscillator are that (1) it uses an LC tuned circuit to establish the frequency of oscillation, (2) feedback is accomplished by mutual inductive coupling between the tickler coil and the LC tuned circuit, and (3) it uses a class C amplifier with self-bias. Its frequency is fairly stable, and the output amplitude is relatively constant. Views (A), (B), and (C) shown in figure 2-10 can be used to build the basic Armstrong oscillator. View (A) shows a conventional amplifier. R2 provides the forward bias for Q1, C2 is a coupling capacitor, and L1 and R1 form the collector load impedance. This is a common-emitter configuration which provides the 180-degree phase shift between the base and collector. Figure 2-10A.—Basic Armstrong oscillator circuit. AMPLIFIER


Electrical News
Your Part in the Recovery
Engineers and innovators are central to the slow but ongoing...
eetimes.com
Motor Controllers Offer Improved Noise Immunity
Operating at 5V gives these digital signal controllers enhanced noise...
eetimes.com
NXP to Pick Up Its Missing IoT Link - Bluetooth Low Energy
In pursuit of the Internet of Things market, NXP Semiconductors...
eetimes.com
USB Oscilloscopes Get Beta Drivers for Open-Source Hardware
Pico Technology has released beta versions of drivers for BeagleBoneBlack...
eetimes.com
It's Alive! The 3D Printing of Living Tissues
Within a generation, we likely will not just hear of...
eetimes.com
Curiosity Killed the Cat (Just Call Me Mr. Curiosity)
Max desperately needs a cat deterrent, but how should this...
eetimes.com
Memory Design Articles: Diagnostics, Datacenters & Failures
Here's a roundup of recent design articles that are relevant...
eetimes.com
Megachips to Launch DSP-Based Sensor Fusion IC
The growing sensor-fusion controller market for smartphones and wearable devices...
eetimes.com
MediaTek Plans $49 Million Investment in China's Chip Fund
Taiwan's largest chip designer has announced it will invest $48.9...
eetimes.com
Reduce Noise When Making M-PHY Measurements
To make useful measurements on M-PHY Gear 3, you need...
eetimes.com
EEVblog #686 – Mailbag
A monster sized high definition 50fps Mailbag, with two special...
eevblog.com
Startup to Open Source Parallel CPU
Rex Computing plans a parallel processor that could deliver a...
eetimes.com
OCZ Cuts Into Read-Intensive SSD Segment
The SATA-based Saber 1000 Series is yet another option in...
eetimes.com
Infotainment Systems Drive Automotive SSD Adoption
In-vehicle entertainment and navigation systems are becoming more mainstream and...
eetimes.com
Scaling Up Text Rendering on Scaled-Down Devices
The need to support a widening range of languages and...
eetimes.com
What Is Design-to-Cost & Why Does It Matter?
Design-to-Cost should be part of your design process. With a...
eetimes.com
Can Japan Get Her Groove Back With IoT?
Japan once looked like a world leader in smart home...
eetimes.com
The 10 Commandments of Electronics
Although these 'commandments' are presented in a humorous manner, they...
eetimes.com
Broadband Demand Hits the High Seas
Cruise ship operators Royal Caribbean and Carnival are exploring new...
eetimes.com
Anritsu ShockLine VNAs Receive Frost & Sullivan Award
Its line of "faceless" VNA used for production RF T&M...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +