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A2E_EETimes_2_375x10.87_A2.qxd 10/29/15 9:07 A U L T R A M I N I A T U R E Surface Mount Audio Transformers and Inductors filter, making the layout less critical, simplifying the choice of inductors, and reducing Low Profile from the number of high quality RF termination resistors required. The diplexer may also be used after a transmission line balun to improve the high .18"frequency behavior of the input network, as well as to reduce the noise bandwidth ht. of an RF gain block. The LTC2107 and a number of other direct sampling ADCs do not perform well if driven by a transmission line transformer in close proximity. If the transmission line transformer is placed more than 6 inches distant from the LTC2107, performance may be acceptable, but the additional space required is rarely acceptable. See full Catalog immediately w ww.pi coelect ronics. co m • Manufactured and tested to MIL-PRF-27 • Frequency range 20 Hz to 250 KHz • Power and EMI Inductors • Available from 100 milliwatts to 3 watts • Impedance from 20 ohms to 100 K ohms • Operating temperature -550C to +130oC (Class V, 155˚C available) • Low Profile from .18"ht. • Thru-Hole available Delivery-Stock to one week for sample quantities PICOElectronics, Inc. 143 Sparks Ave., Pelham, N.Y. 10803 www.picoelectronics.com E Mail: info@picoelectronics.com Pico Representatives Germany ELBV/Elektronische Bauelemente Vertrieb E-mail: info@elbv.de Phone: 0049 89 4602852 Fax: 0049 89 46205442 England Ginsbury Electronics Ltd. E-mail: rbennett@ginsbury.co.uk Phone: 0044 1634 298900 Fax: 0044 1634 290904 Fig. 1: Double-terminated driver for 20MHz to 400MHz. The adverse effects of many transmission line transformers are in part due to asymmetry in the construction of the Guanella balun, unequal line lengths, time skew between the lines in the twisted pair running through the binocular core, and undesired coupling between successive passes through the core, producing return reflections, as well as asymmetry in the returned products. Common mode transients translated to differential form by asymmetrical returns will degrade SFDR. The diplexer will hide this asymmetry from the ADC, allowing use of a single-ended absorptive filter or a single-ended drive amplifier prior to a balun, and allowing these to be closer to the ADC. The diplexer may provide a greater degree of freedom to use flux-coupled transformers that have poor impedance balance above 400MHz. Transformers with extended low frequency response often have too much inter-winding capacitance to perform well with high speed ADCs. Other thin film baluns that do not behave well at high sample rates may be aided by the diplexer. Note that the diplexer does not act as a balun. Drive signals must be amplitude and phase balanced in the passband, as well as being at least nominally absorptive in the region below 500MHz. The use of this diplexer may be advisable if the drive signals for the ADC originate on the other side of a printed circuit board Fig. 2: Source-terminated DC coupled driver for use to 100MHz. www.electronics-eetimes.com Electronic Engineering Times Europe December 2015 41


EETE DEC 2015
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