SL2524B

SL2524 1.3GHz Dual Wideband Logarithmic Amplifier DS4548 - 2.1 July 1995 The SL2524 is a pin compatible replacement for the SL2521 and SL2522 series of log amplifiers, and exhibits a superior stability performance. The amplifier is a successive detection type which provides linear gain and accurate logarithmic signal compression over a wide bandwidth. The two stages can be operated independently. When six stages (three SL2524s) are cascaded the strip can be used for IFs between 30-650MHz whilst achieving greater than 65dB dynamic range with a log accuracy of 65dB of input dynamic range, with pulse handling of better than 25ns. (See figs 5 and 6.) A six stange strip also offers balanced IF limiting, linearity (log accuracy) of < ±1.0dB, temperature stabilisation and programmable detector characteristics. The detector has an external resistor set (RSET) pin which allows the major characteristics of the detector to be programmed. With six stage strip it is possible to vary the value of RSET on each detector and so improve the overall log error/linearity. The detector is full wave and good slew rates are achieved with 2ns rise and 5ns fall times (no video filter). The video bandwidth of a six stage strip is typically 600MHz (-3dB). The amplifier also offers balanced IF limiting, low phase shift versus input amplitude, and at an IF of 120MHz, less than 5° of phase change is achievable over the input level of -55dBm to +5dBm. The IF and Video ports can be used simultaneously, so offering phase, frequency and pulse (video) information. A slight loss of dynamic range (2dB) will be observed when the IF ports are used in conjunction with the video. Fig.4 Test circuit Fig.5 Schematic diagram showing configuration of SD Log strip 5 SL2524 Fig.6 Circuit diagram for 6-log strip (results shown in figs. 11 to 24 were achieved with this circuit) Typical characteristics for a dual - stage amplifier (i.e. One SL2524) Fig.7 IF Gain vs frequency of 2 amplifiers (One SL2524) 6 SL2524 Typical characteristics for a dual - stage amplifier (i.e. One SL2524) cont. Fig.8 Normalised phase vs CW input level at 50, 250 and 450MHz for 50Ω O/P termination (25°C) Fig.9 Detector current vs RSET at 200MHz (25°C) 7 SL2524 Typical characteristics for a dual - stage amplifier (i.e. One SL2524) cont. Fig.10 Detector current vs frequency at RSET = 200Ω and 500Ω (25°C) Typical characteristics for a six stage strip, using detected output (Ref. figs 5 & 6) Fig.11 Detector bandwidth (25°C) 8 SL2524 Typical characteristics for a six stage strip, using detected output (Ref. figs 5 & 6) cont. 0 Fig.12 Detected O/P vs CW input at 60, 125, 450 and 600MHz at 25°C Fig.13 Detected O/P vs CW input level and temperature at 60 and 125MHz 9 SL2524 Typical characteristics for a six stage strip, using detected output (Ref. figs 5 & 6) cont. Fig.14 Detected O/P vs CW input level at 450MHz across temperature Fig.15 Typical log linearity of detected output measured at 450MHz (25°C) 10 SL2524 Typical characteristics for a six stage strip as a low phase shift wideband limiter (Ref. figs 5 & 6) Fig.16 IF limiting characteristics at 60MHz and 500MHz (25°C) Fig.17 IF limiting characteristic at 60MHz across temperature 11 SL2524 Typical characteristics for a six stage strip as a low phase shift wideband limiter (Ref. figs 5 & 6) Fig.18 IF limiting characteristic at 500MHz across temperature Fig.19 Small signal gain vs frequency across temperature 12 SL2524 Typical characteristics for a six stage strip as a low phase shift wideband limiter (Ref. figs 5 & 6) Fig.20 Phase deviation vs CW input level (normalised at -30dBm) at 25°C across input frequency Fig.21 Phase deviation vs CW input level (normalised at -30dBm) at 50MHz across temperature 13 SL2524 Typical characteristics for a six stage strip as a low phase shift wideband limiter (Ref. figs 5 & 6) Fig.22 Phase deviation vs CW input level (normalised at -30dBm) at 450MHz across temperature Fig.23 Peak phase deviation over -65dBm → +10dBm CW input level vs CW input frequency. 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