{"id":1545,"date":"2020-04-23T08:00:06","date_gmt":"2020-04-23T12:00:06","guid":{"rendered":"http:\/\/blog.pasternack.com\/?p=1545"},"modified":"2022-08-05T09:01:01","modified_gmt":"2022-08-05T13:01:01","slug":"what-is-a-variable-gain-amplifier-vca","status":"publish","type":"post","link":"\/blog\/variable-gain-rf-amplifier\/what-is-a-variable-gain-amplifier-vca\/","title":{"rendered":"What is a Variable Gain Amplifier (VGA)?"},"content":{"rendered":"<p><img loading=\"lazy\" decoding=\"async\" class=\"alignright size-full wp-image-1547\" src=\"\/blog\/wp-content\/uploads\/2020\/05\/PE15A7000.jpg\" alt=\"\" width=\"500\" height=\"334\" srcset=\"\/blog\/wp-content\/uploads\/2020\/05\/PE15A7000.jpg 500w, \/blog\/wp-content\/uploads\/2020\/05\/PE15A7000-235x157.jpg 235w, \/blog\/wp-content\/uploads\/2020\/05\/PE15A7000-150x100.jpg 150w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/>A Voltage Variable, variable gain, or voltage controlled amplifier is a type of amplifier with a gain dependent on a control voltage input. These amplifiers are the backbone of amplitude modulation circuits. There are a wide range of types and styles of VCA\u2019s that use various methods of controlling the gain. Some VCAs use voltage control as an input into the feedback network of an amplifier, which then adjusts the gain of the amplifier. A voltage controlled resistor (VCR) could be used within an inverting op-amp\u2019s feedback network to realize a VCA.<\/p>\n<p>Some methods of controlling the gain of an amplifier also have substantial impact on the frequency performance of the device. Hence, it is common to use variable attenuators at the output of the amplifier to control the signal level without changing the frequency performance of the amplifier.<\/p>\n<p>Like with typical amplifiers, VCAs can be made to amplify signals over a wide bandwidth or narrow bandwidth depending on the application. VCAs used in test equipment, military communications, radar testing, and etc. are likely to have extremely wide bandwidths and wide gain variation range, or variable attenuation range. Therefore, wideband VCAs benefit from good gain flatness performance, especially when testing frequency agile radar and wideband communication protocols.<\/p>\n<p>Like with most RF amplifiers, linearity is an important performance feature for VCAs, especially if the application is for instrument test racks or test laboratories. Another critical performance parameter is the noise figure of the VCA, as a high noise figure would limit a VCA\u2019s usefulness in many test scenarios.<\/p>\n<p><strong>Key Variable Gain Amplifier Performance Parameters<\/strong><br \/>\n\u2022 Frequency Range<br \/>\n\u2022 Gain Flatness<br \/>\n\u2022 Input\/Output VSWR<br \/>\n\u2022 Linearity (OP1dB)<br \/>\n\u2022 Gain range or attenuation range<br \/>\n\u2022 Minimum Gain<br \/>\n\u2022 Control features<br \/>\n\u2022 Connectors<br \/>\n\u2022 Gain\/attenuation step size<br \/>\n\u2022 Noise Figure<br \/>\n\u2022 Power supply<\/p>\n<p>VCAs can be controlled using a variable attenuator that is manually controlled, or more sophisticated control can be applied. Some VCAs use analog voltage inputs to control the gain, while others have digital inputs, such as RS-232, to set the gain\/attenuation levels. VCAs with digital control are also called digital variable gain amplifiers (DVGAs).<\/p>\n<p>Thermal management is important for VCAs that operate under high power and high frequency conditions, as much signal energy is converted to heat during normal attenuating operation. Hence, the housing and assembly design must account for this thermal flux created by the unit. This is why wide bandwidth and high frequency VCAs with wide gain\/attenuation ranges are often assembled as rack-mount units and other formats that are suited for integration thermal management systems.<\/p>\n<p>Learn more about Pasternack\u2019s Variable Gain Amplifier offering here: <a href=\"https:\/\/www.pasternack.com\/50-db-gain-variable-gain-amplifier-rack-mount-6.5-db-sma-pe15a7000-p.aspx\"><span style=\"color: #0000ff;\">https:\/\/www.pasternack.com\/50-db-gain-variable-gain-amplifier-rack-mount-6.5-db-sma-pe15a7000-p.aspx<\/span><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>A Voltage Variable, variable gain, or voltage controlled amplifier is a type of amplifier with a gain dependent on a control voltage input. These amplifiers are the backbone of amplitude modulation circuits. There are a wide range of types and styles of VCA\u2019s that use various methods of controlling the gain. Some VCAs use voltage ..<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[195],"tags":[576,577],"class_list":["post-1545","post","type-post","status-publish","format-standard","hentry","category-variable-gain-rf-amplifier","tag-variable-gain-amplifier","tag-vca"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>What is a Variable Gain Amplifier (VGA)? - Pasternack Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"\/blog\/variable-gain-rf-amplifier\/what-is-a-variable-gain-amplifier-vca\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What is a Variable Gain Amplifier (VGA)? - Pasternack Blog\" \/>\n<meta property=\"og:description\" content=\"A Voltage Variable, variable gain, or voltage controlled amplifier is a type of amplifier with a gain dependent on a control voltage input. These amplifiers are the backbone of amplitude modulation circuits. There are a wide range of types and styles of VCA\u2019s that use various methods of controlling the gain. 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