Electronic Components Datasheet Search |
|
EL4430 Datasheet(PDF) 8 Page - Elantec Semiconductor |
|
EL4430 Datasheet(HTML) 8 Page - Elantec Semiconductor |
8 / 12 page EL4430CEL4431C Video Instrumentation Amplifiers Applications Information The EL4430 and EL4431 are designed to convert a fully differential input to a single-ended output It has two sets of inputs one which is connected to the signal and does not respond to its com- mon-mode level and another which is used to complete a feedback loop with the output Here is a typical connection 4430 – 2 The gain of the feedback divider is H The trans- fer function of the part is VOUT e AO c ((VINa) b (VINb) a (VREF b VFB)) VFB is connected to VOUT through a feedback network so VFB e H c VOUT AO is the open- loop gain of the amplifier and is about 600 for the EL4430 and EL4431 The large value of AO drives (VINa) b (VINb) a (VREF b VFB) x0 Rearranging and substituting for VFB VOUT e ((VINa) b (VINb) a VREF )H Thus the output is equal to the difference of the VIN’s and offset by VREF all gained up by the feedback divider ratio The input impedance of the FB terminal (equal to RIN of the input termi- nals) is in parallel with an RG and raises circuit gain slightly The EL4430 is stable for a gain of 1 (a direct connection between VOUT and FB) or more and the EL4431 for gains of 2 or more It is important to keep the feedback divider’s impedance at the FB terminal low so that stray capacitance does not diminish the loop’s phase margin The pole caused by the parallel of resistors RF and RG and stray capacitance should be at least 200 MHz typical strays of 3 pF thus require a feedback im- pedance of 270 X or less Two 510X resistors are acceptable for a gain of 2 300 X and 2700X make a good gain-of-10 divider Alternatively a small capacitor across RF can be used to create more of a frequency-compensated divider The value of the capacitor should scale with the parasitic ca- pacitance at the FB terminal input It is also practical to place small capacitors across both the feedback resistors (whose values maintain the de- sired gain) to swamp out parasitics For instance two 10 pF capacitors (for a gain of 2) across equal divider resistors will dominate parasitic effects and allow a higher divider resistance Input Connections The input transistors can be driven from resistive and capacitive sources but are capable of oscilla- tion when presented with an inductive input It takes about 80nH of series inductance to make the inputs actually oscillate equivalent to 4 of unshielded wiring or about 6 of unterminated input transmission line The oscillation has a characteristic frequency of 500 MHz Often plac- ing one’s finger (via a metal probe) or an oscillo- scope probe on the input will kill the oscillation Normal high-frequency construction obviates any such problems where the input source is rea- sonably close to the input If this is not possible one can insert series resistors of approximately 51 X to de-Q the inputs Signal Amplitudes Signal input common-mode voltage must be be- tween (Vb)a3V and (Va)b3V to ensure linear- ity Additionally the differential voltage on any input stage must be limited to g6V to prevent damage The differential signal range is g2V in the EL4430 and EL4431 The input range is sub- stantially constant with temperature The Ground Pin The ground pin draws only 6 mA maximum DC current and may be biased anywhere between (Vb)a25V and (Va)b35V The ground pin is connected to the IC’s substrate and frequency compensation components It serves as a shield within the IC and enhances CMRR over frequen- cy and if connected to a potential other than ground it must be bypassed 8 |
Similar Part No. - EL4430 |
|
Similar Description - EL4430 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |