TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 1 post office box 655303 ? dallas, texas 75265 low output common-mode sensitivity to agc voltages input and output impedances independent of agc voltage peak gain . . . 38 db typ wide agc range . . . 50 db typ 3-db bandwidth . . . 50 mhz other characteristics similar to ne592 and ua733 description this device is a monolithic two-stage high- frequency amplifier with differential inputs and outputs. internal feedback provides wide bandwidth, low phase distortion, and excellent gain stability. variable gain based on signal summation provides large agc control over a wide bandwidth with low harmonic distortion. emitter-follower outputs enable the device to drive capacitive loads. all stages are current-source biased to obtain high common-mode and supply-voltage rejection ratios. the gain may be electronically attenuated by applying a control voltage to the agc pin. no external compensation components are required. this device is particularly useful in tv and radio if and rf agc circuits, as well as magnetic-tape and disk-file systems where agc is needed. other applications include video and pulse amplifiers where a large agc range, wide bandwidth, low phase shift, and excellent gain stability are required. the TL026c is characterized for operation from 0 c to 70 c. absolute maximum ratings over operating free-air temperature range (unless otherwise noted) 2 supply voltage, v cc+ (see note 1) 8 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . supply voltage, v cc (see note 1) 8 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . differential input voltage 5 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . common-mode input voltage 6 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . output current 10 ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . continuous total dissipation see dissipation rating table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . operating free-air temperature range 0 c to 70 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . storage temperature range 65 c to 150 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lead temperature range 1,6 mm (1/16 inch) from case for 10 seconds 260 c . . . . . . . . . . . . . . . . . . . . . . . . . . 2 stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating o nly, and functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditi ons section of this specification is not implied. exposure to absolute-maximum-rated conditions for extended periods may affect device reliabi lity. note 1: all voltages are with respect to the midpoint of v cc+ and v cc except differential input and output voltages. dissipation rating table package t a 25 c power rating operating factor above t a = 25 c t a = 70 c power rating d 725 mw 5.8 mw/ c 464 mw p 1000 mw 8.0 mw/ c 640 mw copyright ? 1990, texas instruments incorporated production data information is current as of publication date. products conform to specifications per the terms of texas instruments standard warranty. production processing does not necessarily include testing of all parameters. in ref out v cc + out 1 2 3 4 8 7 6 5 in+ agc v cc out+ d or p package (top view) symbol + agc in + in 7 4 5 2 1 8 ref out out+ out
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 2 post office box 655303 ? dallas, texas 75265 recommended operating conditions min nom max unit supply voltage, v cc + 3 6 8 v supply voltage, v cc 3 6 8 v operating free-air temperature range, t a 0 70 c electrical characteristics at 25 c operating free-air temperature, v cc+ = 6 v, v agc = 0, ref out pin open (unless otherwise specified) parameter figure test conditions min typ max unit a vd large-signal differential voltage amplification 1 v o(pp) = 3 v, r l = 2 k w 65 85 105 v/v d a vd change in voltage amplification 1 v ipp = 28.5 mv, r l = 2 k w, v agc v ref = 180 mv 50 db v ref voltage at ref out i ref = 1 ma to 100 m a 1.3 1.5 v bw bandwidth ( 3 db) 2 v o(pp) = 1 v, v agc v ref = 180 mv 50 mhz i io input offset current 0.4 5 m a i ib input bias current 10 30 m a v icr common-mode input voltage range 3 1 v v oc common-mode output voltage 1 r l = 3.25 3.75 4.25 v d v oc change in common-mode output voltage 1 v agc = 0 to 2 v, r l = 300 mv v oo output offset voltage 1 v id = 0, r l = 0.75 v v o(pp) maximum peak-to-peak output voltage swing 1 r l = 2 k w 3 4 v r i input resistance at agc, in+, or in 10 30 k w r o output resistance 20 w cmrr common mode rejection ratio 3 v ic = 1 v, f = 100 khz 60 86 db cmrr common - mode rejection ratio 3 v ic = 1 v, f = 5 mhz 60 db k svr supply voltage rejection ratio ( d v cc / d v io ) 4 d v cc + = 0.5 v, d v cc = 0.5 v 50 70 db v n broadband equivalent noise voltage 4 bw = 1 khz to 10 mhz 12 m v t pd propagation delay time 2 d v o = 1 v 6 10 ns t r rise time 2 d v o = 1 v 4.5 12 ns i sink(max) maximum output sink current v id = 1 v, v o = 3 v 3 4 ma i cc supply current no load, no signal 22 27 ma
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 3 post office box 655303 ? dallas, texas 75265 electrical characteristics over recommended operating free-air temperature range, v cc = 6 v, v agc = 0, ref out pin open (unless otherwise specified) parameter figure test conditions min typ max unit a vd large-signal differential voltage amplification 1 v o(pp) = 3 v, r l = 2 k w 55 115 v/v i io input offset current 6 m a i ib input bias current 40 m a v icr common-mode input voltage range 3 1 v v oo output offset voltage 1 v id = 0, r l = 1.5 v v o(pp) maximum peak-to-peak output voltage swing 1 r l = 2 k w 2.8 v r i input resistance at agc, in+, or in 8 k w cmrr common-mode rejection ratio 3 v ic = 1 v, f = 100 khz 50 db k svr supply voltage rejection ratio ( d v cc / d v io ) 4 d v cc + = 0.5 v, d v cc = 0.5 v 50 db i sink(max) maximum output sink current v id = 1 v, v o = 3 v 2.8 4 ma i cc supply current 1 no load, no signal 30 ma parameter measurement information in + in agc out + out ref out r l 50 w 50 w v oc v o v o 2 + v agc v ref v id v od figure 1. test circuit 1 k w 1 k w v o + v o 50 w 50 w + v id 0.2 m f 0.2 m f figure 2. test circuit 1 k w 1 k w v o + v o 50 w 50 w + 0.2 m f 0.2 m f v ic figure 3. test circuit r l = 2 k w + v od figure 4. test circuit
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 4 post office box 655303 ? dallas, texas 75265 typical characteristics figure 5 200 100 0 100 200 a differential voltage amplification vs differential gain-control voltage vd v agc v ref differential gain-control voltage mv 100 90 80 70 60 50 40 30 20 10 0 v cc + = 6 v v cc = 6 v t a = 0 c t a = 70 c t a = 25 c e differential voltage amplification e v/ v
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 5 post office box 655303 ? dallas, texas 75265 application information gain characteristics figure 5 shows the differential voltage amplification versus the differential gain-control voltage (v agc v ref ). v agc is the absolute voltage applied to the a gc input and v ref is the dc voltage at the ref out output. as v agc increases with respect to v ref , the TL026c gain changes from maximum to minimum. as shown in figure 5 for example, v agc would have to vary from approximately 180 mv less than v ref to approximately 180 mv greater than v ref to change the gain from maximum to minimum. the total signal change in v agc is defined by the following equation. d v agc = v ref + 180 mv (v ref 180 mv) d v agc = 360 mv (1) however, because v agc varies as the ac agc signal varies and also differentially around v ref , then v agc should have an ac signal component and a dc component. to preserve the dc and thermal tracking of the device, this dc voltage must be generated from v ref . to apply proper bias to the agc input, the external circuit used to generate v agc must combine these two voltages. figures 6 and 7 show two circuits that will perform this operation and are easy to implement. the circuits use a standard dual operational amplifier for agc feedback. by providing rectification and the required feedback gain, these circuits are also complete agc systems. circuit operation amplifier a1 amplifies and inverts the rectified and filtered agc signal voltage v c producing output voltage v1. amplifier a2 is a differential amplifier that inverts v1 again and adds the scaled v ref voltage. this conditioning makes v agc the sum of the signal plus the scaled v ref . as the signal voltage increases, v agc increases and the gain of the TL026c is reduced. this maintains a constant output level. feedback circuit equations following the agc input signal (figures 6 and 7) from the out output through the feedback amplifiers to the agc input produces the following equations: (2) 1. ac ouput to diode d1, assuming sinusoidal signals v o = v op (sin (wt)) where: v op = peak voltage of v o (3) 2. diode d1 and capacitor c1 output v c = v op v f where: vf = forward voltage drop of d1 v c = voltage across capacitor c1 (4) 3. a1 output v1 r2 r1 v c (5) 4. a2 output (r3 = r4) v agc r2 r1 v c 2 r6 r5 r6 v ref
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 6 post office box 655303 ? dallas, texas 75265 application information amplifier a2 inverts v1 producing a positive agc signal voltage. therefore, the input voltage to the TL026c agc pin consists of an agc signal equal to: (6) r2 r1 v c and a dc voltage derived from v ref , defined as the quiescent value of v agc . v agc (q) 2 r6 r5 r6 v ref (7) for the initial resistor calculations, v ref is assumed to be typically 1.4 v making quiescent v agc approximately 1.22 v (v agc (q) = v ref 180 mv). this voltage allows the TL026c to operate at maximum gain under no-signal and low-signal conditions. in addition, with v ref used as both internal and external reference, its variation from device to device automatically adjusts the overall bias and makes agc operation essentially independent of the absolute value of v ref . the resistor divider needs to be calculated only once and is valid for the full tolerance of v ref . output voltage limits (see figures 6 and 7) the output voltage level desired must fall within the following limits: 1. because the data sheet minimum output swing is 3 v peak-to-peak using a 2-k w load resistor, the user-selected design limit for the peak output swing should not exceed 1.5 v. 2. the voltage drop of the rectifying diode determines the lower voltage limit. when a silicon diode is used, this voltage is approximately 0.7 v. the output voltage v o must have sufficient amplitude to exceed the rectifying diode drop. aschottky diode can be used to reduce the v o level required. gain calculations for a peak output voltage of 1 v a peak output voltage of 1 v was chosen for gain calculations because it is approximately midway between the limits of conditions 1 and 2 in the preceding paragraph. using equation 3 (v c = v op v d ), v c is calculated as follows: v c = 1 v 0.7 v v c = 0.3 v therefore, the gain of a1 must produce a voltage v1 that is equal to or greater than the total change in v agc for maximum TL026c gain change. with a total change in v agc of 360 mv and using equation 4, the calculation is as follows: v1 v c v agc v c r2 r1 0.36 0.3 1.2 if r1 is 10 k w , r2 is 1.2 time r1 or 12 k w . since the output voltage for this circuit must be between 0.85 v and 1.3 v, the component values in figures 6 and 7 provide a nominal 1-v peak output limit. this limit is the best choice to allow for temperature variations of the diode and minimum output voltage specification.
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 7 post office box 655303 ? dallas, texas 75265 application information the circuit values in figures 6 and 7 will produce the best results in this general application. because of rectification and device input constraints, the circuit in figure 6 will not provide attenuation and has about 32 db of control range. the circuit shown in figure 7 will have approximately 25% variation in the peak output voltage limit due to the variation in gain of the tl592 device to device. in addition, if a lower output voltage is desired, the output of the TL026c can be used for approximately 40 mv of controlled signal. considerations for the use of the TL026c to obtain the most reliable results, rf breadboarding techniques must be used. a groundplane board should be used and power supplies should be bypassed with 0.1- m f capacitors. input leads and output leads should be as short as possible and separated from each other. a peak input voltage greater than 200 mv will begin to saturate the input stages of the TL026c and, while the circuit is in the agc mode, the output signal may become distorted. to observe the output signal of TL026c or tl592, low-capacitance fet probes or the output voltage divider technique shown in figure 6 should be used. + + out + out 0.1 m f 0.1 m f ref out 30 k w to scope monitor v out 200 w 1.8 k w in in + 50 w agc 10 k w 10 k w v agc a2 20 k w 50 w v i + 10 k w a1 12 k w 1n914 d1 0.1 m f v1 1/2 tl082 1/2 tl082 TL026c note: v cc + = 6 v and v cc = 6 v for TL026c and amplifiers a1 and a2. figure 6. typical application circuit with no attenuation
TL026c differential high-frequency amplifier with agc slfs007a june 1985 revised july 1990 8 post office box 655303 ? dallas, texas 75265 application information + r6 20 k w 50 w 0.1 m f v out v out + 0.1 m f a1 50 w 10 k w r1 12 k w r2 1/2 tl082 0.1 m f out out + in in + agc to scope monitor + a2 10 k w r4 1/2 tl082 30 k w r5 10 k w r3 v agc v i 1.8 k w 200 w 1n914 ref out TL026c 0.1 m f tl592 2 k w 2 k w 510 w + + x20 gain note: v cc + = 6 v and v cc = 6 v for TL026c and amplifiers a1 and a2. figure 7. typical application circuit with attenuation
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